Catch my Point

Using themed css files requires a header control on the page. (e.g. ).

If you get above error that means

1. you tag in web.config and
2. you don't have "head" tag with "runat" attribute in the web page.

Fix: Ofcourse put below tag in the web page but many a times probably you don't the HEAD tag in your web response esp. like Ajax requests or RSS pages then just set visible="false" that should fix the problem. I hoped EnableTheming="false" attribute in the Page tag will fix this problem but it didn't work for me let me know if there is any other solution for this!!!