Here are the simple steps to debug js code in your aspx markup. 1. Open Visual Studio 2008/2010 2. Click Tools then options 3. Expand debugging node then click checkboxes Manages,Native,Script. 4. In your web.config file,make sure to set compilation debug to true. <compilation debug= "true" > <assemblies> <add assembly= "System.Core, Version=3.5.0.0, Culture=neutral, PublicKeyToken=B77A5C561934E089" /> <add assembly= "System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" /> <add assembly= "System.Data.DataSetExtensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=B77A5C561934E089" /> <add assembly= "System.Xml.Linq, Version=3.5.0.0, Culture=neutral, PublicKeyToken=B77A5C561934E089" /> </assemblies> </compilation> 5. Choo