1.
If you are on .net 4.0 make sure you add this in your web.config
<httpRuntime requestValidationMode=”2.0″ />

2.
myTextBox.Text = Server.HtmlEncode(myStringFromDatabase);

MyLabel.Text = HttpUtility.HtmlEncode(MyTextBox.Text)

3. To disable request validation on a page add the following directive to the existing “page” directive in the file (you will need to switch to the HTML view for this):
ValidateRequest=”false”