Question: I've just installed Visual Studio 2010, but I cant seem to manage to get intellisense working to suggest classes.

Answer: 
Make sure to try and click "ctrl+space" to force intellisense
Create a simple .aspx webform, drag and drop from the solution explorer the .css file. Go to source view and write something like this:

```
<span class="

```

then normally you should get intellisense. Same goes for the CssClass properties for server controls.

If you however try to include your .css file in a dynamic way by code then you could end up not getting intellisense.