PageSpeed Completely Messed Up Page

[mobysmokem]

I ran the test twice. Once on aggressive, once on safe.

The aggressive one was a huge improvement in speed but messed up the results - eg: a div broke my CSS - I have no idea why.

The "safe" resulted in BLANK. That's right, a blank video with both the original and the "improved" version.

What exactly is the problem with PageSpeed and what should one watch out for. Are there any things that are problematic? I have js stuff on my page, resizing etc - it's not a simple html page. I this problematic?

Thanks