Have you heard of W3C? Otherwise known as the World Wide Web Consortium (W3C), they exist to develop interoperable technologies (specifications, guidelines, software, and tools) to lead the Web to its full potential. W3C is a forum for information, commerce, communication, and collective understanding.
Two very useful features of the W3C site are the CSS Validator and the HTML Validator.
If you are not a coder and you want to learn more about what your code does and what errors exist – this is a great resource.
You don’t need to know about code to appreciate the complexity in why things don’t work the way they should. Often something doesn’t work because a sloppily-written plugin is causing problems, or your attempt at hacking your way through your own CSS results in errors.
Here are some screenshots of the Validators’ results:

I also recommend surfing through the Glossary pages. There are terms bandied about that have many meanings and this site is the closest to the actual meaning you will find. Here is a page about web accessibility.
Other CSS Validators, Compressors, Simplification Programs
I don’t know which one I used once upon a time, but somebody in the Thesis Theme Forum suggested I use it to simplify my CSS and it did wonders. It took over 200 lines of code to about 80 and it did the trick beautifully. I also then understood where I went wrong – lots of unnecessary duplication on my part. I would love to recommend this site but cannot remember which one it was nor what the link is.
If you know of sites that provide free programs to paste your CSS code sheet into and get a polished version after clicking a button – please let us know below in the comments.
