A potentially dangerous Request.Form value was detected from the client

I had a run time error on my web application last week . It was a request form application whichhas user input testboxes. When I looked into event viewer on the server, the actual problem was:

A Potentially dangerous Request.Form value was detected from the client.

Basically it means that you can't post values containing HTML ( or script ) tags to the server.

In other words - if you have a textbox and the visitor enters something like :

and then presses Submit button this error will occur since the posted value(s) contains HTML tags.

There are different solutions to solve thhis problem, you can read more at ASP.Net site. Many People suggests changing web.config file which is a bad solutions since it'll affect all pages on your Site.

The simple solution is add a tag validateRequest="false" into the Page-directive on top of the page. When request validation is disabled, content can be submitted to a page but developer should ensure that content is properly encoded or processed.

Happy Programming!!