If I am not wrong then you want to know the programming language used for a site by just looking at its URL.
Yes that is possible, and by looking at the extension of the file that is loading we can guess the programming language.
For e. g. if you see at URL of any page on this forum, then the extension used is . php, meaning this forum is developed using . php.
The same techniques goes for others. The . net site will have extension as . aspx and for classic asp sites the extension will be . asp
Hope that helps you.
And what if when extension is not show in url many of this type of sites available in which extension is not shown.