In asp.net C# sometimes we get potentially dangerous Request error. potentially dangerous Request error comes when we try to pass special character's like <,>,:...etc. In order to solve the potentially dangerous Request error we need to set validateRequest="false" in page directive for perticular page like:
<%@ Page Language="C#" AutoEventWireup="true" <b>ValidateRequest="false"</b>%>
Or if we want to set it for whole web application page then we can set it in web.config in
<pages smartNavigation="false" <b>validateRequest="false"</b> enableSessionState="true"></pages>
If we are using newer version of .net framework then we need to set "requestValidationMode="2.0"" in "
<httpRuntime maxRequestLength="10000" executionTimeout="3600" <b>requestValidationMode="2.0"</b>/>