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Dear Sir,

Recently in one of my website gives error as follows:
HTTP Error 503. Service Unavailable.

And in IIS 7 application pool is stop automatically for the website.
I have restart the pool but when I run the website it goes to stop.

I googled it, follow the below steps but could not solve the problem.

1.Custom account issue.To change username and password for application pool in IIS 7.
-There is no such username or password for my website.

2.In application pool,Advanced setting--Rapid Fail Protection --Maximum Failures 50
- No change in Error.
3.Change of application pool, I have created new application pool and run website using that pool but the same error.

Please guide me useful steps to resolve this issue.

Updated 7-Dec-17 5:34am
ZurdoDev 9-Aug-12 16:32pm    
This can happen when there is more than one site in the app pool and they are using different versions of .Net. Also, what is in the event viewer?
hiteshprajpati 14-Aug-12 5:33am    
The event viewer gives following error:--
The worker process failed to pre-load .Net Runtime version v4.0.20506.

Now this problem is solved.
By using .Net framework cleanup tool.
I have uninstall .net framework 4.0 then re-install it.

Also I have read articles for this error each article gives some useful suggestion so it helps a lot to understand the problem and how to solve it.

This link is very much useful for above error.
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I have solved it changing in th pool advanced settings the identity due to my password has been expired so i upgraded it to my actual password and it worked again!
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vijaysutaria 29-May-17 1:12am    
Thanks for the help.
Member 14669810 12-Feb-20 1:42am    
Thank You, This solution resolved my problem
I installed and ran the .NET repair tool from the Microsoft download site and this fixed the problem of the default application pool stopping automatically after many frustrated minutes of trying to find a solution elsewhere on the net.
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