classpath error

Hi All

i got the classpath error when i build the project.seethe following error.

<b>The project was not built since its classpath is incomplete. Cannot find the class file for com.sapportals.portal.prt.component.AbstractPortalComponent. Fix the classpath then try rebuilding this project.</b>

can u tell me where to give the classpath which is incomplete?

pls help

Regards

Sunil