IIS 6.0 Prompts "Server application is not available" solution _win Server

Today, on the company test server put 2 test sites, IIS actually reported that the server application is not available, the IIS restarted, the application pool is also recycled, the site folder permissions have also changed, incredibly still not, well, the following how we solve.

Error message:

Server application not Available
The Web application you are attempting to access on this Web server is currently unavailable. Please click the "Refresh" button in the Web browser to retry your request.
Administrator considerations: The error message detailing the reason for this particular request failure can be found in the WEB server's system event log. Please check this log entry to find out why this error occurred.

Solution:
need to re-register. NET in IIS

Copy Code code as follows:

CD c:\windows\microsoft.net\framework\v2.0.50727 (please fill in the version number) \

aspnet_regiis.exe/i

Aspnet_regiis-r

As shown in figure