Board Thread:Support Requests - Getting Technical/@comment-5111231-20170716210132/@comment-9605025-20170716221112

First, if I were you, I would make sure to not violate the Customization Policy.

I am not entirely certain what you are referring to when you are talking about "tag/modules"; however, I will assume you are talking about things such as ".WikiHeaderRestyle" and ".navbackground". In that case, these are called selectors. You can see a reference of available selectors here. As for the particular examples, they are class selectors. They select an element based on the HTML class attribute. The syntax is ".class" were "class" is replaced with the relevant value. There is no pre-defined set of classes so there is no standard documentation. Wikia could provide documentation on the classes it uses but it does not. I suspect the reason is that the classes tend to change whenever they make updates. The best way to figure out which class you want to target is to use your web browser to inspect the HTML it receives. Unfortunately, this usually cannot be done on mobile devices.

The website I linked to is pretty helpful when getting started with CSS. Nonetheless, some users disparage it because it has some inaccuracies and is not the official documentation. For the official documentation, go to w3.