During my time on here, I have seen many people have problems with code. If you would like to learn how to fix some of these problems for yourself, then I will show you some examples. The main errors I see are:
1) Sections of info boxes sticking out from the rest of the box.
2) The whole page (or parts) getting squished into the info box.
3) The "rich text error".
Most people think they need to remake their page when these happen. Especially 2) and 3). In the following images, I show what is wrong and how to fix it. I also explain why it gives an error.
If you have any other errors you would like to see, or if you find errors on other pages that are not listed here, just let me know and I'll add them. Hope this helps! :)