validateRequest in Umbraco v4

In Umbrao v4 validateRequest=false in web.config has no effect. Instead you should on your user control in Page_Init do the following:

((umbraco.UmbracoDefault)Page).ValidateRequest = false;

For more see this post on the Umbraco Forum:
http://forum.umbraco.org/yaf_postst7313_usercontrol-and-ValidateRequest.aspx