Error: The Web Server Could Not Find the Requested Resource while debugging the web application you might receive this type of error after you update the web application tools

Reason :
If you have installed the URLScan Filter this error will come , basically URLScan is for IIS 7 if you install for IIS 6 it will create this problem .

Solution:
Un install the URLScan Tool , Because IIS 6 has all the resources of URLScan