I figured it out!!!

You were right leocg!

This youtube downloader was a virus that messed with how opera read CSS.
https://addons.opera.com/en/extensions/details/free-youtube-mp3-downloader/?display=en

I disabled and removed the extension and now everything works right.

Disabled all extensions and re added them one at a time till i found it.

Those pages seem to be working here. Have you checked with the extensions disabled?

What extensions?

Its not an add-on. Its a CSS issue. Dont have anything to do with extensions.

I have the same problem, but worse with Opera 27.0.1689.69. Win 7 32

In this Example from above it wont even load the CSS output. In fact, the buttons on the bottom of CodePen dont work either.

This Screenshot is my Opera.
This Screenshot is in Firefox and all the functions work correctly.

It is the same case for the other 2 examples "meakl" posted above.

The site i used to upload the pics (http://www.imagesup.net/) i even had to use in Firefox because it didnt work in Opera.

I just figured out what the problem actually was so im not sure when it started.

CSS animations and buttons not always displaying correctly for me.
I just figured out CSS was the issue so Im not exactly sure when it started but its been recently.

This page does not display the output preview and the buttons at the bottom of the page dont work either.
http://codepen.io/kieranfivestars/pen/gbOWbM

This is a screenshot of mine.
http://www.imagesup.net/?di=314239482210

This screenshot is in Firefox and all animation/buttons work.
http://www.imagesup.net/?di=11142394822112

The case is the same for these 2 examples too.
http://codepen.io/chrisota/pen/ByaZME
http://codepen.io/Responsive/pen/raNrEW

In fact, http://www.imagesup.net didnt work in my opera either but was fine in Firefox.
Thats just 2 sites. There are dozens of pages that dont work.

It used to work then after a recent update it stopped.

How do i fix it?