hundreds of errors in VS2008

In Visual Studio 2008 I see hundreds of errors within my开发者_StackOverflow中文版 web app. If I open the offending page(s) within VS, I'll see dozens of items underlined in red - then the errors resolve themselves.

Any idea why this happens and how to resolve it?

I used to get this all the time, sometimes the DLL's referenced to create ASP.NET web controls take VS a little while to resolve the controls contained within them - aka any ASP controls.

Really, I don't think there's anyway to fix it. If you just wait and ignore it the problem should fix itself.