These days users face 500 internal server problem in India (users in West Bengal and TamilNadu). It mostly happens with BSNL (Bharat Sanchar Nigam Ltd.) users. While opening sites like Google, YouTube, Wikipedia. This is definitely annoying for the users.
According to this article of About.com
The 500 Internal Server Error is a “server-side” error, meaning the problem is not with your PC or Internet connection but instead is a problem with the web site’s server.
500 internal server is problem related to server side but how can the problem occurred with all the top sites of the world? Definitely there is some flaw in the whole procedure. Either your browser is showing you the fake 500 error or it is something else which is beyond my knowledge.
Amit of Ampercent.com tested the things on his computer and came out with a nice result. According to him, the problem was in the DNS . After changing the DNS to Google DNS, he succeeded to open all the websites properly. It might be possible that DNS provided by his ISP unable to convert the domain name address into IP-address and returning that error.
Check out the nice step by step tutorial to change the DNS server address to solve the 500 internal server error.