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1、220CHAPTER7■SEARCHENGINEOPTIMIZATIONCorrectlySignaling404and500ErrorsItisimportanttousethecorrectHTTPstatuscodewhensomethingspecialhappenstothevisitor’srequest.You’vealreadyseenthat,whenperformingredirects,knowledgeofHTTPstatuscodescanmakeanimportantdiff
2、erencetoyourSEOefforts.Thistimewewilltalkabout404and500.The404statuscodeisusedtotellthevisitorthatheorshehasrequestedapagethatdoesn’texistonthedestinationwebsite.Browsersandwebservershavetemplatesthatusersgetwhenyoumakesucharequest—youknow,you’veseenthem
3、.Hostingservicesletyouspecifyacustompagetobedisplayedwhensucha404erroroccurs.Thisisobviouslybeneficialforyoursite,asyoucanprovidesomecustomfeedbacktoyourvisitordependingonwhatheorshewassearchingfor.Sometimes,however,the404statuscodeisn’tautomaticallysetf
4、oryou,soyouneedtodoitinyour404script.If,forsomereason,yoursitereactsto404errorsbysendingpageswiththe200OKstatuscode,searchengineswillthinkthatyouhavemanydifferentURLshostingthesamecontent,andyoursitemaygetpenalized.We’llbeusingthe404statusmessageinthefol
5、lowingcircumstances:•Whenthevisitorrequestsapagethatdoesnotexistinourwebsite•WhenthevisitorrequestsaproductwithanIDthatdoesnotexistinourdatabaseThe500statusmessageisusedtocommunicatethatthewebserverortheapplicationishavinginternalerrors.Rightnow,whensuch
6、aninternalerroroccurs,BalloonShopservesOops.aspx,butfailstocorrectlysetthe500statuscode.ThisisproblematicbecauseifGoogleindexesthesitewhenthesitefacestechnicalerrors,itwillgetalotofidenticalpagesmarkedas“good”withthe200statuscode,replacingtheirpreviously
7、indexedversions.Inthefollowingexercise,we’llcustomizeBalloonShoptousethe404and500statuscodescorrectly.Exercise:Usingthe500HTTPStatusCode1.AddanewWebFormtoyoursite,namedNotFound.aspx.Don’tuseacode-behindfile—insteadusetheBalloonShop.masterMasterPage,andal
8、terthegeneratedcodeasfollows:<%@PageLanguage="C#"MasterPageFile="~/BalloonShop.master"➥Title="BalloonShop:Whatareyoulookingfor?"%>protectedvoidPageLoad(objectsender,EventArgse){//setthe404statuscodeRe
