Website Looks strange in browsers other than Chrome

Greetings, my site looks fine, with the latest changes to pages and posts reflecting correctly in Chrome. But when I test them in IE or Firefox, they look like old pages and also look downright bad.

For a little background, a while ago my site was a total mess and my theme (optimize press) tech support did a rebuild for me. This happened after a major wordpress update at the time, I think version 4.0.

I recently installed WP Super Cache in hopes of deleting any cached pages and hopefully rebuild the cache so that hopefully they will look better in other browsers, and nothing.

In other words, I am not sure if what I did helped. Or do I just wait a little longer?

I deleted a plugin called ‘Autoptimize’, Frank the author is a very nice guy, but he suggested I delete the existing cache (I ave no idea where to find it and delete it), and then find out where all the old autoptimize files went? Or how they were deleted. My guess is they got deleted during the rebuild that my theme tech support did.

Anyways, at this point I am struggling to solve this. Some pages look terrible in IE and Firefox, and I had a hello bar plugin which I have now deactivated, but it still shows up in IE/Firefox. Chrome is OK, but maybe it will also show me problems if I delete history and cache? Don’t know yet, but will test it.

Any help is much appreciated.

My site: https://www.stressebook.com

Best,
Surya.