I am faceing problem with this error

I am using Struts application while running welcome page is run successfully after that the following error is appear

description :The s开发者_JAVA技巧erver encountered an internal error () that prevented it from fulfilling this request. eception

org.apache.jasper.JasperException: Failed to load or instantiate TagLibraryValidator class: org.apache.taglibs.standard.tlv.JstlCoreTLV

any idea whats the problem.

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Do two things:

1)check classpath

2)check that standard.jar is added in WEB-INF/lib.