OReilly HTML and XHTML the definitive guide 5th edition aug 2002 ISBN 059600382x

Tableof
•
Contents
• Index
• Reviews
• Examples
Reader
•
Reviews
• Errata

HTML&XHTML:TheDefinitiveGuide,
5thEdition
ByBillKennedy,ChuckMusciano

Publisher :O'Reilly
PubDate :August2002
ISBN :0-596-00382-X
Pages :670
Slots :1
HTML&XHTML:TheDefinitiveGuide,5thEditionisthe
mostcomprehensive,up-to-datebookavailableonHTML
andXHTML.Theauthorscovereveryelementof
HTML/XHTMLindetail,explaininghoweachelement
worksandhowitinteractswithotherelements.With
hundredsofexamples,thebookgivesyoumodelsfor
writingyourowneffectivewebpagesandformastering
advancedfeatureslikestylesheetsandframes.

HTML&XHTML:TheDefinitiveGuide,
5thEdition

ByBillKennedy,ChuckMusciano
Tableof
•
Contents Publisher :O'Reilly
PubDate :August2002
• Index
ISBN :0-596-00382-X
• Reviews
Pages :670
Slots :1
• Examples
Reader
•
Reviews
• Errata



Copyright

Dedication



Preface



OurAudience



TextConventions



VersionsandSemantics



HTMLVersusXHTML



CommentsandQuestions



Acknowledgments

Chapter1.HTML,XHTML,andtheWorldWideWeb



Section1.1.TheInternet



Section1.2.TalkingtheInternetTalk



Section1.3.HTMLandXHTML:WhatTheyAre



Section1.4.HTMLandXHTML:WhatTheyAren't



Section1.5.StandardsandExtensions



Section1.6.ToolsfortheWebDesigner

Chapter2.QuickStart



Section2.1.WritingTools



Section2.2.AFirstHTMLDocument



Section2.3.EmbeddedTags



Section2.4.HTMLSkeleton



Section2.5.TheFleshonanHTMLorXHTMLDocument

Section2.6.Text



Section2.7.Hyperlinks



Section2.8.ImagesAreSpecial



Section2.9.Lists,SearchableDocuments,andForms



Section2.10.Tables



Section2.11.Frames



Section2.12.StyleSheetsandJavaScript



Section2.13.ForgingAhead

Chapter3.AnatomyofanHTMLDocument



Section3.1.AppearancesCanDeceive



Section3.2.StructureofanHTMLDocument



Section3.3.TagsandAttributes



Section3.4.Well-FormedDocumentsandXHTML



Section3.5.DocumentContent



Section3.6.HTML/XHTMLDocumentElements

Section3.7.TheDocumentHeader



Section3.8.TheDocumentBody



Section3.9.EditorialMarkup



Section3.10.The<bdo>Tag




Chapter4.TextBasics



Section4.1.DivisionsandParagraphs



Section4.2.Headings

Section4.3.ChangingTextAppearanceandMeaning



Section4.4.Content-BasedStyleTags



Section4.5.PhysicalStyleTags



Section4.6.PreciseSpacingandLayout



Section4.7.BlockQuotes



Section4.8.Addresses



Section4.9.SpecialCharacterEncoding



Section4.10.HTML'sObsoleteExpandedFontHandling

Chapter5.Rules,Images,andMultimedia



Section5.1.HorizontalRules



Section5.2.InsertingImagesinYourDocuments



Section5.3.DocumentColorsandBackgroundImages



Section5.4.BackgroundAudio



Section5.5.AnimatedText



Section5.6.OtherMultimediaContent

Chapter6.LinksandWebs



Section6.1.HypertextBasics



Section6.2.ReferencingDocuments:TheURL



Section6.3.CreatingHyperlinks




Section6.4.CreatingEffectiveLinks



Section6.5.Mouse-SensitiveImages



Section6.6.CreatingSearchableDocuments

Section6.7.Relationships



Section6.8.SupportingDocumentAutomation




Chapter7.FormattedLists



Section7.1.UnorderedLists



Section7.2.OrderedLists



Section7.3.The<li>Tag



Section7.4.NestingLists

Section7.5.DefinitionLists



Section7.6.AppropriateListUsage



Section7.7.DirectoryLists



Section7.8.MenuLists




Chapter8.CascadingStyleSheets



Section8.1.TheElementsofStyles



Section8.2.StyleSyntax



Section8.3.StyleClasses

Section8.4.StyleProperties



Section8.5.TaglessStyles:The<span>Tag



Section8.6.ApplyingStylestoDocuments




Chapter9.Forms



Section9.1.FormFundamentals



Section9.2.The<form>Tag



Section9.3.ASimpleFormExample

Section9.4.UsingEmailtoCollectFormData



Section9.5.The<input>Tag



Section9.6.The<button>Tag



Section9.7.MultilineTextAreas



Section9.8.MultipleChoiceElements



Section9.9.GeneralForm-ControlAttributes



Section9.10.LabelingandGroupingFormElements

Section9.11.CreatingEffectiveForms



Section9.12.FormsProgramming




Chapter10.Tables



Section10.1.TheStandardTableModel



Section10.2.BasicTableTags



Section10.3.AdvancedTableTags



Section10.4.BeyondOrdinaryTables

Chapter11.Frames




Section11.1.AnOverviewofFrames



Section11.2.FrameTags



Section11.3.FrameLayout



Section11.4.FrameContents



Section11.5.The<noframes>Tag



Section11.6.InlineFrames



Section11.7.NamedFrameorWindowTargets

Chapter12.ExecutableContent



Section12.1.AppletsandObjects



Section12.2.EmbeddedContent



Section12.3.JavaScript



Section12.4.JavaScriptStyleSheets(Antiquated)




Chapter13.DynamicDocuments



Section13.1.AnOverviewofDynamicDocuments

Section13.2.Client-PullDocuments



Section13.3.Server-PushDocuments




Chapter14.NetscapeLayoutExtensions



Section14.1.CreatingWhitespace



Section14.2.MulticolumnLayout



Section14.3.Layers




Chapter15.XML

Section15.1.LanguagesandMetalanguages



Section15.2.DocumentsandDTDs



Section15.3.UnderstandingXMLDTDs



Section15.4.ElementGrammar



Section15.5.ElementAttributes



Section15.6.ConditionalSections



Section15.7.BuildinganXMLDTD

Section15.8.UsingXML




Chapter16.XHTML



Section16.1.WhyXHTML?



Section16.2.CreatingXHTMLDocuments



Section16.3.HTMLVersusXHTML



Section16.4.XHTML1.1



Section16.5.ShouldYouUseXHTML?

Chapter17.Tips,Tricks,andHacks



Section17.1.TopoftheTips



Section17.2.CleaningUpAfterYourHTMLEditor



Section17.3.TrickswithTables




Section17.4.TransparentImages



Section17.5.TrickswithWindowsandFrames




AppendixA.HTMLGrammar

SectionA.1.GrammaticalConventions



SectionA.2.TheGrammar




AppendixB.HTML/XHTMLTagQuickReference



SectionB.1.CoreAttributes



SectionB.2.HTMLQuickReference




AppendixC.CascadingStyleSheetPropertiesQuickReference



AppendixD.TheHTML4.01DTD

AppendixE.TheXHTML1.0DTD



AppendixF.CharacterEntities



AppendixG.ColorNamesandValues



SectionG.1.ColorValues



SectionG.2.ColorNames



SectionG.3.TheStandardColorMap




Colophon

Index


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Whileeveryprecautionhasbeentakeninthepreparationofthisbook,
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containedherein.


Dedication
Thisbookisdedicatedtoourwivesandchildren,Cindy,Courtney,
andCole,andJeanne,Eva,andEthan.Withouttheirloveand

patience,weneverwouldhavehadthetimeorstrengthtowrite.


Preface
LearningHypertextMarkupLanguage(HTML)andExtensibleHypertext
MarkupLanguage(XHTML)islikelearninganynewlanguage,computer
orhuman.Moststudentsfirstimmersethemselvesinexamples.Studying
othersisanaturalwaytolearn,makinglearningeasyandfun.Our
advicetoanyonewantingtolearnHTMLandXHTMListogetoutthere
ontheWebwithasuitablebrowserandseeforyourselfwhatlooksgood,
what'seffective,andwhatworksforyou.Examineothers'documentsand
ponderthepossibilities.Mimicryishowmanyofthecurrentwebmasters
havelearnedthelanguage.
Imitationcantakeyouonlysofar,though.Examplescanbebothgood
andbad.Learningbyexamplehelpsyoutalkthetalk,butnotwalkthe
walk.Tobecometrulyconversant,youmustlearnhowtousethe
languageappropriatelyinmanydifferentsituations.Youcouldlearnall
thatbyexample,ifyoulivelongenough.
Remember,too,thatcomputer-basedlanguagesaremoreexplicitthan
humanlanguages.Youhavetogetthelanguagesyntaxcorrectoritwon't
work.Thenthereistheproblemof"standards."Committeesof
academicsandindustryexpertsdefinethepropersyntaxandusageofa
computerlanguagelikeHTML.Theproblemisthatbrowser
manufacturerslikeNetscapeCommunicationsCorporation(anAmerica
Onlinecompany)andMicrosoftCorporationchoosewhichpartsofthe
standardtheywilluseandwhichpartstheywillignore.Theyevenmake
uptheirownparts,whichmayeventuallybecomestandards.
Standardschange,too.HTMLisundergoingaconversionintoXHTML,
makingitanapplicationoftheExtensibleMarkupLanguage(XML).
HTMLandXHTMLaresosimilarthatweoftenrefertothemasasingle

language,buttherearekeydifferences,whichwediscusslaterinthis
Preface.
Tobesafe,thewaytobecomefluentinHTMLandXHTMListhrougha
comprehensive,up-to-datelanguagereferencethatcoversthelanguage


syntax,semantics,andvariationsindetailtohelpyoudistinguish
betweengoodandbadusage.
There'sonemorestepleadingtofluencyinalanguage.Tobecomea
truemasterofthelanguage,youneedtodevelopyourownstyle.That
meansknowingnotonlywhatisappropriate,butwhatiseffective.Layout
matters.Alot.Sodoestheorderofpresentationwithinadocument,
betweendocuments,andbetweendocumentcollections.
OurgoalinwritingthisbookistohelpyoubecomefluentinHTMLand
XHTML,fullyversedintheirsyntax,semantics,andelementsofstyle.
Wetakethenaturallearningapproach,usingexamples(goodones,of
course).Wecoverindetaileveryelementofthecurrentlyaccepted
standardversionsofthelanguages(HTML4.01andXHTML1.0)aswell
asallofthecurrentextensionssupportedbythepopularbrowsers,
explaininghoweachelementworksandhowitinteractswithallofthe
otherelements.
And,withallduerespecttoStrunkandWhite,throughoutthebookwe
giveyousuggestionsforstyleandcompositiontohelpyoudecidehow
besttouseHTMLandXHTMLtoaccomplishavarietyoftasks,from
simpleonlinedocumentationtocomplexmarketingandsales
presentations.Weshowyouwhatworksandwhatdoesn't,whatmakes
sensetothosewhoviewyourpages,andwhatmightbeconfusing.
Inshort,thisbookisacompleteguidetocreatingdocumentsusing
HTMLandXHTML,startingwithbasicsyntaxandsemantics,and
finishingwithbroadstyleguidelinestohelpyoucreatebeautiful,

informative,accessibledocumentsthatyou'llbeproudtodelivertoyour
readers.


OurAudience
Wewrotethisbookforanyoneinterestedinlearningandusingthe
languageoftheWeb,fromthemostcasualusertothefull-timedesign
professional.Wedon'texpectyoutohaveanyexperienceinHTMLor
XHTMLbeforepickingupthisbook.Infact,wedon'tevenexpectthat
you'veeverbrowsedtheWeb,althoughwe'dbeverysurprisedifyou
haven't.BeingconnectedtotheInternetisnotstrictlynecessarytouse
thisbook,butifyou'renotconnected,thisbookbecomeslikeatravel
guideforthehomebound.
Theonlythingsweaskyoutohaveareacomputer,atexteditorthatcan
createsimpleASCIItextfiles,andcopiesofthelatestleadingweb
browsers--preferablyNetscapeNavigatorandInternetExplorer.
BecauseHTMLandXHTMLdocumentsarestoredinauniversally
acceptedformat--ASCIItext--andbecausethelanguagesare
completelyindependentofanyspecificcomputer,wewon'tevenmake
anassumptionaboutthekindofcomputeryou'reusing.However,
browsersdovarybyplatformandoperatingsystem,whichmeansthat
yourHTMLorXHTMLdocumentscanlookquitedifferentdependingon
thecomputerandbrowserversion.Weexplainhowthevariousbrowsers
usecertainlanguagefeatures,payingparticularattentiontohowtheyare
different.
IfyouarenewtoHTML,theWeb,orhypertextdocumentationingeneral,
youshouldstartbyreadingChapter1.Init,wedescribehowallthese
technologiescometogethertocreatewebsofinterrelateddocuments.
IfyouarealreadyfamiliarwiththeWeb,butnotwithHTMLorXHTML
specifically,startbyreadingChapter2.Thischapterisabriefoverviewof

themostimportantfeaturesofthelanguageandservesasaroadmapto
howweapproachthelanguageintheremainderofthebook.
Subsequentchaptersdealwithspecificlanguagefeaturesinaroughly
top-downapproachtoHTMLandXHTML.Readtheminorderfora
completetourthroughthelanguage,orjumparoundtofindtheexact


featureyou'reinterestedin.


TextConventions
Throughoutthebook,weuseaconstant-widthtypefacetohighlight
anyliteralelementoftheHTML/XHTMLstandards,tags,andattributes.
Wealwaysuselowercaselettersfortags.[1]Weuseitalicforfilenames
andURLsandtoindicatenewconceptswhentheyaredefined.Elements
youneedtosupplywhencreatingyourowndocuments,suchastag
attributesoruser-definedstrings,appearinconstant-widthitalic
inthecode.
[1]HTMLiscase-insensitivewithregardtotagandattributenames,butXHTMLiscasesensitive.AndsomeHTMLitems,suchassourcefilenames,arecase-sensitive,sobe
careful.

Wediscusselementsofthelanguagethroughoutthebook,butyou'llfind
eachonecoveredindepth(somemightsayinnauseatingdetail)ina
shorthand,quick-referencedefinitionboxthatlooksliketheonethat
follows.Thefirstlineoftheboxcontainstheelementname,followedbya
briefdescriptionofitsfunction.Next,welistthevariousattributes,ifany,
oftheelement:thosethingsthatyoumayormustspecifyaspartofthe
element.

<title>
Function
Definesthedocumenttitle
Attributes
dirlang
Endtag
</title>;neveromitted
Contains
plain_text
Usedin
head_content

Weusethefollowingsymbolstoidentifytagsandattributesthatarenot
intheHTML4.01orXHTML1.0standardsbutareadditionstothe
languages:
Netscapeextensiontothestandards
InternetExplorerextensiontothestandards
Thedescriptionalsoincludestheendingtag,ifany,fortheelement,
alongwithageneralindicationofwhethertheendtagmaybesafely
omittedingeneraluseinHTML.Forthefewtagsthatrequireendtagsin
XHTMLbutdonothavetheminHTML,thelanguageletsyouindicate
thatbyplacingaforwardslash(/)beforethetag'sclosingbracket,asin

.Inthesecases,thetagmayalsocontainattributes,indicated
withaninterveningellipsis,suchas.
The"Contains"headernamestheruleintheHTMLgrammarthatdefines


theelementstobeplacedwithinthistag.Similarly,the"Usedin"header
liststhoserulesthatallowthistagaspartoftheircontent.Theserules
aredefinedinAppendixA.

Finally,HTMLandXHTMLarefairlyintertwinedlanguages.Youwill
occasionallyuseelementsindifferentwaysdependingoncontext,and
manyelementsshareidenticalattributes.Whereverpossible,weplacea
cross-referenceinthetextthatleadsyoutoarelateddiscussion
elsewhereinthebook.Thesecross-references,liketheoneattheendof
thisparagraph,serveasacrudepapermodelofhypertext
documentation,onethatwouldbereplacedwithatruehypertextlink
shouldthisbookbedeliveredinanelectronicformat.[Section3.3.1]
Weencourageyoutofollowthesereferenceswheneverpossible.Often,
wecoveranattributebrieflyandexpectyoutojumptothecrossreferenceforamoredetaileddiscussion.Inothercases,followingthelink
takesyoutoalternativeusesoftheelementunderdiscussionortostyle
andusagesuggestionsthatrelatetothecurrentelement.


VersionsandSemantics
ThelatestHTMLstandardisVersion4.01,butmostupdatesand
changestothelanguagestandardweremadeinVersion4.0.Therefore,
throughoutthebook,wegenerallyrefertotheHTMLstandardasHTML
4,encompassingVersions4.0andlater.Weexplicitlystatethe"dot"
versionnumberonlywhenitisrelevant.
TheXHTMLstandardiscurrentlyinitsfirstiteration,1.0.Asecond
version(XHTML1.1)hasbeenproposedbutnotyetestablished.Forthe
mostpart,XHTML1.0isidenticaltoHTML4.01;wedetailtheir
differencesinChapter16.Throughoutthebook,wespecificallynote
caseswhereXHTMLhandlesafeatureorelementdifferentlythanthe
originallanguage,HTML.
TheHTMLandXHTMLstandardsmakeveryclearthedistinction
between"elementtypes"ofadocumentandthemarkup"tags"that
delimitthoseelements.Forexample,thestandardreferstothe
paragraphelementtype,whichisnotthesameasthe

tag.The

paragraphelementconsistsoftheacceptedelement-typenamewithin
thestartingtag(

),interveningcontent,andtheendingparagraphtag
(

).The

tagisthestartingtagfortheparagraphelement,andits
contents,knownasattributes,ultimatelyaffecttheparagraphelement
type'scontents.
Althoughtheseareimportantdistinctions,we'repragmatists.Itisthe
markuptagthatauthorsapplyintheirdocumentsandthataffectsany
interveningcontent.Accordingly,throughoutthebook,werelaxthe
distinctionbetweenelementtypesandtags,oftentalkingabouttagsand
allrelatedcontentsandnotnecessarilyusingtheterm"element-type"
whenitwouldbetechnicallyappropriatetomakethedistinction.Forgive
usthetransgression,butwedosoforthesakeofclarity.


HTMLVersusXHTML
It'snotLatin,butHTMLhasreachedmiddleageinstandardVersion
4.01.TheW3Chasnoplanstodevelopanotherversionandhasofficially
saidso.Rather,HTMLisbeingsubsumedandmodularizedasan
ExtensibleMarkupLanguage(XML).ItsnewnameisXHTML,Extensible
HypertextMarkupLanguage.
TheemergenceofXHTMLisjustanotherchapterintheoftentumultuous
historyofHTMLandtheWeb,whereconfusionforauthorsisthenorm,
nottheexception.Attheworstpoint,theeldersoftheWorldWideWeb
Consortium(W3C)responsibleforacceptedandacceptableusesofthe
language--i.e.,standards--lostcontrolofthelanguageinthebrowser
"wars"betweenNetscapeandMicrosoft.TheabortiveHTML+standard
nevergotofftheground,andHTML3.0becamesoboggeddownin
debatethattheW3Csimplyshelvedtheentiredraftstandard.HTML3.0
neverhappened,despitewhatsomeopportunisticmarketersclaimedin
theirliterature.Instead,bylate1996,thebrowsermanufacturers

convincedtheW3CtoreleaseHTMLstandardVersion3.2,whichforall
intentsandpurposessimplystandardizedmostofNetscape'sHTML
extensions.
Netscape'sdominanceastheleadingbrowser,aswellasaleaderin
Webtechnologies,fadedbytheendofthemillennium.Bythen,Microsoft
hadeffectivelybundledInternetExplorerintotheWindowsoperating
system,notonlyasaninstalledapplication,butalsoasadominant
featureoftheGUIdesktop.And,too,InternetExplorerintroducedseveral
features(albeitnonstandardatthetime)thatappealedprincipallytothe
growingInternetbusinessandmarketingcommunity.
Fortunatelyforthoseofuswhoappreciateandstronglysupport
standards,theW3CtookbackitsprimacyrolewithHTML4.0,which
standstodayasHTMLVersion4.01,releasedinDecember1999.
AbsorbingmanyoftheNetscapeandInternetExplorerinnovations,the
standardisclearerandcleanerthananypreviousones,establishessolid
implementationmodelsforconsistencyacrossbrowsersandplatforms,


providesstrongsupportandincentivesforthecompanionCascading
StyleSheets(CSS)standardforHTML-baseddisplays,andmakes
provisionsforalternative(nonvisual)useragents,aswellasformore
universallanguagesupports.
Cleanerandcleareraside,theW3CrealizedthatHTMLcouldneverkeep
upwiththedemandsofthewebcommunityformorewaystodistribute,
process,anddisplaydocuments.HTMLoffersonlyalimitedsetof
document-creationprimitivesandishopelesslyincapableofhandling
nontraditionalcontentlikechemicalformulae,musicalnotation,or
mathematicalexpressions.Norcanitwellsupportalternativedisplay
media,suchashandheldcomputersorintelligentcellularphones.
Toaddressthesedemands,theW3CdevelopedtheXMLstandard.XML

providesawaytocreatenew,standards-basedmarkuplanguagesthat
don'ttakeanactoftheW3Ctoimplement.XML-compliantlanguages
deliverinformationthatcanbeparsed,processed,displayed,sliced,and
dicedbythemanydifferentcommunicationtechnologiesthathave
emergedsincetheWebsparkedthedigitalcommunicationrevolutiona
decadeago.XHTMLisHTMLreformulatedtoadheretotheXML
standard.ItisthefoundationlanguageforthefutureoftheWeb.
WhynotjustdropHTMLforXHTML?Formanyreasons.Firstand
foremost,XHTMLhasnotexactlytakentheWebbystorm.There'sjust
toomuchcurrentinvestmentinHTML-baseddocumentationand
expertiseforthattohappenanytimesoon.Besides,XHTMLisHTML
4.01reformulatedasanapplicationofXML.KnowHTML4andyou'reall
readyforthefuture.[2]
[2]WeplumbthedepthsofXMLandXHTMLinChapter15andChapter16.

DeprecatedFeatures
Oneoftheunpopularthingsstandards-bearershavetodoismake
choicesbetweenpopularandproper.TheauthorsoftheHTMLand
XHTMLstandardsexercisethatresponsibilityby"deprecating"those
featuresofthelanguagethatinterfereinthegrandschemeofthings.


Forinstance,thetagtellsthebrowsertodisplaytheenclosed
textcenteredinthedisplaywindow.ButtheCSSstandardprovidesways
tocentertext,too.TheW3CchoosestosupporttheCSSwayand
discouragestheuseofbydeprecatingthetag.Theplanis,in
somelaterstandardversion,tostopusingandother
deprecatedelementsandattributesofthelanguage.
Throughoutthebook,wespeciallynoteandcontinuouslyremindyou
whenanHTMLtagorothercomponentisdeprecatedinthecurrent

standards.Shouldyoustopusingthemnow?Yesandno.
Yes,becausethereisapreferredandperhapsbetterwaytoaccomplish
thesamething.Byexercisingthatalternative,youensurethatyour
documentswillsurviveformanyyearstocomeontheWeb.And,yes,
becausethetoolsyoumayusetoprepareHTML/XHTMLdocuments
probablyadheretothepreferredstandard.Youmaynothaveachoice,
unlessyoudisableyourtools.Inanyevent,unlessyouhand-composeall
yourdocuments,you'llneedtoknowhowthepreferredwayworkssothat
youcanidentifythecodeandmodifyit.
Howevercompellingthereasonsfornotusingdeprecatedelementsand
attributesare,theystillarepartofthestandards.Theyremainwell
supportedbymostbrowsersandaren'texpectedtodisappearanytime
soon.Infact,sincethereisnoplantochangetheHTMLstandard,the
"deprecated"stampisverymisleading.
So,no,youdon'thavetoworryaboutdeprecatedHTMLfeatures.There
isnoreasontopanic,certainly.Weencourageyoutouseandcontinueto
usethem,sincethedeprecatedfeaturestypicallyaresimplerand
eminentlymorehuman-readablethantheiralternatives.

ADefinitiveGuide
TheparadoxinallthisisthateventheHTML4.01standardisnotthe
definitiveresource.TherearemanymorefeaturesofHTMLinpopular
useandsupportedbythepopularbrowsersthanareincludedinthe
latestlanguagestandard.Andtherearemanypartsofthestandardsthat


areignored.Wepromiseyou,thingscangetdownrightconfusing.
We'vemanagedtosortthingsoutforyou,though,soyoudon'thaveto
sweatoverwhatworksanddoesn'tworkwithwhatbrowser.Thisbook,
therefore,isthedefinitiveguidetoHTMLandXHTML.Wegivedetailsfor

alltheelementsoftheHTML4.01andXHTML1.0standards,plusthe
varietyofinterestingandusefulextensionstothelanguage--some
proposedstandards--thatthepopularbrowsermanufacturershave
chosentoincludeintheirproducts,suchas:
CascadingStyleSheets
JavaandJavaScript
Layers
Multiplecolumns
Andwhilewetellyouabouteachandeveryfeatureofthelanguage,
standardornot,wealsotellyouwhichbrowsersordifferentversionsof
thesamebrowserimplementaparticularextensionandwhichdon't.
That'scriticalknowledgewhenyouwanttocreatewebpagesthattake
advantageofthelatestversionofNetscapeversuspagesthatare
accessibletothelargernumberofpeopleusingInternetExploreroreven
Lynx,aonce-populartext-onlybrowserforUnixsystems.
Inaddition,thereareafewthingsthatarecloselyrelatedbutnotdirectly
partofHTML.Forexample,wetouch,butdonothandle,JavaScript,
CGI,andJavaprogramming.TheyallworkcloselywithHTML
documentsandrunwithoralongsidebrowsers,buttheyarenotpartof
thelanguageitself,sowedon'tdelveintothem.Besides,theyare
comprehensivetopicsthatdeservetheirownbooks,suchasJavaScript:
TheDefinitiveGuide,byDavidFlanagan,CGIProgrammingwithPerl,by
ScottGuelich,ShishirGundavaram,andGuntherBirzneiks,Cascading
StyleSheets:TheDefinitiveGuide,byEricMeyer,andLearningJava,by
PatNiemeyerandJonathanKnudsen(allpublishedbyO'Reilly).
ThisisyourdefinitiveguidetoHTMLandXHTMLastheyareandshould


beused,includingeveryextensionwecouldfind.Someextensionsaren't
documentedanywhere,evenintheplethoraofonlineguides.But,if

we'vemissedanything,certainlyletusknowandwe'llputitinthenext
edition.


CommentsandQuestions
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Acknowledgments
Wedidnotcompose,andcertainlycouldnothavecomposed,thisbook
withoutgenerouscontributionsfrommanypeople.Ourwives,Jeanne
andCindy,andourchildren,Eva,Ethan,Courtney,andCole(they
happenedbeforewestartedwriting),formedthefrontlinesofsupport.
Andtherearenumerousneighbors,friends,andcolleagueswhohelped
bysharingideas,testingbrowsers,andlettingususetheirequipmentto
exploreHTML.Youknowwhoyouare,andwethankyouall.

Inaddition,wethankourtechnicalreviewers,EricMeyer,PatNiemeyer,
RobertEckstein,KaneScarlett,EricRaymond,andChrisTacy,for
carefullyscrutinizingourwork.Wetookmostofyourkeensuggestions.
WeespeciallythankMikeLoukides,oureditor,whohadtobringtobear
hisvastexperienceinbookpublishingtokeepustwomavericks
corralled.AndspecialthankstoDebCameronforherperseveranceand
insightinbringingboththefourthandnowthisfiftheditiontofruition.


Chapter1.HTML,XHTML,andtheWorldWide
Web
Thoughitbeganasamilitaryexperimentandspentitsadolescenceasa
sandboxforacademicsandeccentrics,inlessthanadecadethe
worldwidenetworkofcomputernetworks--alsoknownastheInternet
hasmaturedintoahighlydiversified,financiallyimportantcommunityof
computerusersandinformationvendors.Fromtheboardroomtoyour
livingroom,youcanbumpintoInternetusersofnearlyanyandall
nationalities,ofanyandallpersuasions,fromserioustofrivolous
individuals,frombusinessestononprofitorganizations,andfrombornagainChristianevangeliststopornographers.
Inmanyways,theWebtheopencommunityofhypertext-enabled
documentserversandreadersontheInternetisresponsibleforthe
meteoricriseinthenetwork'spopularity.You,too,canbecomeavalued
memberbycontributing:writingHTMLandXHTMLdocumentsandthen
makingthemavailabletowebsurfersworldwide.
Let'sclimbuptheInternetfamilytreetogainsomedeeperinsightintoits
magnificence,notonlyasanexerciseofcuriosity,buttohelpusbetter
understandjustwhoandwhatitiswearedealingwithwhenwego
online.

1.1TheInternet
Althoughpopularmediaaccountsareoftenconfusedandconfusing,the
conceptoftheInternetreallyisrathersimple:it'saworldwidecollection
ofcomputernetworksanetworkofnetworkssharingdigitalinformation
viaacommonsetofnetworkingandsoftwareprotocols.
Networksarenotnewtocomputers.WhatmakestheInternetuniqueis
itsworldwidecollectionofdigitaltelecommunicationlinksthatsharea
commonsetofcomputer-networktechnologies,protocols,and
applications.WhetheryourunMicrosoftWindowsXP,Linux,MacOSX,
oreventhenowancientWindows3.1,whenconnectedtotheInternet,
computersallspeakthesamenetworkinglanguageandusefunctionally
identicalprograms,soyoucanexchangeinformationevenmultimedia
picturesandsoundwithsomeonenextdoororacrosstheplanet.
Thecommonandnowquitefamiliarprogramspeopleuseto
communicateanddistributetheirworkovertheInternethavealsofound
theirwayintoprivateandsemi-privatenetworks.Theseso-called
intranetsandextranetsusethesamesoftware,applications,and
networkingprotocolsastheInternet.ButunliketheInternet,intranetsare
privatenetworks,withaccessrestrictedtomembersoftheinstitution.
Likewise,extranetsrestrictaccessbutusetheInternettoprovide
servicestomembers.
TheInternet,ontheotherhand,seeminglyhasnorestrictions.Anyone
withacomputerandtherightnetworkingsoftwareandconnectioncan
"getontheNet"andbeginexchangingwords,sounds,andpictureswith
othersaroundtheworld,dayornight:nomembershiprequired.And
that'spreciselywhatisconfusingabouttheInternet.
Likeanorientalbazaar,theInternetisnotwellorganized,therearefew
contentguides,anditcantakealotoftimeandtechnicalexpertisetotap
itsfullpotential.That'sbecause...

1.1.1IntheBeginning