We are sending an HTML encoded string in the Query string. It was working fine on IIS 6 (windows 2003). We have recently moved the website to Windows 2008 (IIS 7.x). Since t
The reason why you are facing this error is that IIS7 has introduced new URL filtering rules for security reasons.
So '+' sign is blocked by default as part of security reason in URL.
To resolve this issue you have to set allowDoubleEscaping="true" in web.config files.
Here is the tag to do that.