Error-‘unable to find script library '/aspnet_client/system_web/1_1_4322/WebUIValidation.js’
This error mostly occur if you are using validation controls in your website.The aspnet_client folder contains the WebUIValidation.js which is required to handle the asp.net validation controls.
To resolve this, you may need to run the following from command prompt
This will install the aspnet_client folder to the default virtual directory website.
if you are still having this issue try following:
a) Another potential cause of this error is that your default website is set to .NET Framework 2.0, and you're trying to debug a .NET Framework 1.1 application. In this case, you can change the setting on the ASP.NET tab of the Default Web Site's properties
b)Check if the script files directory(/aspnet_client/system_web/1_1_4322/) in IIS manager to see whether it has been granted read access / check the folder permissions