If you have adopted beta 2 of Visual Studio 2010 then you might have spotted a large amount of green squigglies underneath the tags in your markup. When you have over them you see a message like this:
Validation ($SCHEMA$): Element 'div' is not supported
This appears to be a bug in the system. When this is occurring your autocomplete will not have any html element – only asp.net controls and snippets – which makes it pretty hard to do your work.
Unfortunately this is one of the aspects of using beta software. There is a fix but it can be annoying if you customize your environment a lot.
To get rid of the errors temporarily (it seems to come back every time I load VS2010) you have to reset the configuration to factory defaults by doing the following:
1. In Visual Studio 2010 Beta 2 click Tools | Import and Export Settings...
4. The final window lets you decide the default collection of settings you want to apply. This is the choice you are presented with the first time you run visual studio and it includes the new code-focused web development profile which has been added to vs2010. Make a selection and click Finish.
5. Visual studio will now apply the settings you have made and present you with a final results screen. Click the close button to return to your IDE.
6. After a short pause the system will refresh itself and all of the green squigglies will be gone.
For me this error seems to keep coming back - I haven't spotted if this is occurring every time I boot or if it is occurring randomly but if this is happening to you then now you have the solution!