Board Thread:Support Requests - Designing Your Wiki/@comment-36535642-20191228142729/@comment-9605025-20191229054733

This article gives a pretty good explanation of. It makes even more sense of you read this article as well.

When conflicting values for a given CSS property apply to the same HTML element, there needs to be a way to decide which one gets applied. The process can be roughly summarized as follows.
 * 1) Take note of the competing value assignments for a particular property.
 * 2) Do any of the assignments use ? If yes, ignore assignments that do not use   when performing the remaining steps.
 * 3) Do any of them happen in-line? If yes, ignore assignments that do not happen in-line when performing the remaining steps and jump to step #6.
 * 4) Determine the specificity associated with each assignment.
 * 5) Determine the highest specificity among the assignments. Ignore assignments that do not have the highest specificity when performing the remaining steps.
 * 6) Use the assignment that appears last in the stylesheet/style attribute.

The bottom line is that using  when it isn't necessary can force it to be necessary later on. In the context of FANDOM wikis, this issue most commonly manifests itself as future CSS changes and personal CSS not working as expected. The only common case (as far as I can tell) where you would actually need to use it on a wiki is when you are trying to override in-line CSS. In-line CSS is CSS added to an element's  attribute either directly in the markup or by JS. Here is an example of in-line CSS directly in the markup. This box is 150x150 px with a red background and a blue border. This box is 150x150 px with a red background and a blue border.

Fortunately, your wiki doesn't have much CSS yet. I have seen some wikis that have hundreds of lines of CSS with seemingly at least half of the lines using.

Looking at your current CSS, it appears you have one use in Wikia.css and two uses in Common.css. As a side note, there is no practical difference between Wikia.css and Common.css so you might want to consider keeping everything on one page. The two uses in Common.css are note needed; you can remove them and the CSS will still work as expected. That is not true for the use in Wikia.css. In cases where  appears to be needed, you should try to increase the specificity of your selector instead (see the second article for more on specificity). Note that your current Wikia.css violates the customization policy since it changes the link colors in the navigation bar as well as other "do not touch" portions of the page.