cvc-elt.1: Cannot find the declaration of element 'web-app'

早上启动eclipse某项目报错提示：cvc-elt.1: Cannot find the declaration of element 'web-app'；

昨个儿还正常，今儿就不行了？

难道是直接强关电脑造成的？

but，i have the answer!!!

This worked for me:

the relevant option is at Window->Preferences->General->Network Connections->Cache->Disable Caching. Check that box, then clean and build.