Content outside </HTML> tag after update of theme's CSS.

All right, so I started a new job that has a site through Drupal which I've used before with success after initial setup.
A strange thing happened today, when I uploaded the site's theme .css with more correct responsive format for modern phones.... An orphan (for lack of a better word) html tag has now been posted at the bottom of the website, under the footer.

It's like:

</html>
<p><img src="..."</img></p> 

on EVERY SINGLE DRUPAL site.

I have cleared the cache's from the administration, performance menu -- I've restored the backed up .css file back and I still have this random paragraph tag driving me nuts. Is there any area in Drupal's file structure that I could be missing that would tell it to place a HTML tag out side the last line? I've seen the flexibility of using blocks to edit areas of the page; but this does not fit inside a block-- it's like an orphan line.

Any tips or information would be greatly appreciated -- maybe there is something I'm overlooking.

Thanks!