You can check
the post of Web Developer team for more detailed info.
Here are few RadControls related details:
...
| Issue | Many NBSPs added and tag name corruption when
editing a page that uses Telerik controls (popular custom controls) |
| Description | When there are multiple register directives
for the same namespace in different assemblies, multiple NBSPs may be generated
in your page and your markup could possibly be changed incorrect. This can be
seen when using some Telerik controls. |
| Resolution | VS no longer changes your code
incorrectly |
| Link | http://forums.asp.net/t/1185266.aspx |
...
| Issue | Telerik Controls Not Working in Visual Studio
2008 |
| Description | Some telerik control configuration aren’t
working properly in all cases in VS2008. Specifically, if you click on the
RadAjaxManager and click Configure Ajax Manager, you will get an empty
collection when you inherit from a master page. |
| Resolution | You now get the appropriate collection when
using this configuration utility. |
| Link | http://www.telerik.com/community/forums/thread/b311D-bbgthd.aspx |
Enjoy!