On our company website most links are in the form:

http://www.foobar.com/contact.html

Is it a better idea to have 

http://www.foobar.com/contact

Or does it not matter. I got thinking because when I was submitting a form at google adsense it refused to let me have a "." in the sub-page link modifier (see below "Path" box).
 

Thoughts?

[![enter image description here][1]][1]


  [1]: https://i.sstatic.net/HIuXX.png