Scenario/problem: Browse service.asmx on localhost and click on any webmethod, you get error as shown below.
Solution: This problem may be due to many reasons.
1..NET Framework version 2.0 and 1.1 by default disables web services HTTP GET, HTTP POST and SOAP protocols. Click here to see details on how to enable this http://support.microsoft.com/default.aspx?scid=kb;en-us;819267
2.After making changes mentioned above, if problem persist than add all protocols in web.config to get exact error. Hopefully this will give you exact error details