Microsoft JScript runtime error: 'Sys' is undefined

After some time back was working in a Development project and was came across an error :

Microsoft JScript runtime error: 'Sys' is undefined,

as i went on hunting for the solution for this there are so many answers i was able to find. But the error which was triggerd in my application was due to not specifying httphandlers and httpmodules handlers in web.conf file.

I will try to post the code later as for the moment i couldn't post html stuffs in blogger.