Thanks 02audionoob and recoveryone

I did play with with browser's zoom feature and no matter what settings I use, the web browser still retained its 16:9 ratio which I think answered my question. I was guessing that browser ratio would change with different resolution setting, but it seem the 16:9 ratio stay the same and only thing that changed was web pages lay out.

I am guessing they design most web pages based on 1360x768 ratio since at that resolution, one don't have to use the bottom scroller to to see the whole page horizontally. Any lower resolution and one have to use to mouse to move page from right to left to see the whole page.