Help:Lint errors/obsolete-tag

The obsolete-tag error is when deprecated HTML elements are used. Currently, the deprecated elements with their alternatives are:

Font sizes
The values above seven are equivalent to seven.

Rationale
Mediawiki currently whitelists these elements, and they tend to be output the same way as input. This means that when browser vendors decide to remove these they will simply display as regular undecorated text. Examples of some "popular" html tags that had visual effects and have been removed from major browsers include  and. A further problem is that different browser vendors may remove them independently so editors or readers may have inconsistent views of the same page, leading to confusion.

Such removal of styling or unique treatment of html tags by browser vendors can happen at any time and without prior notice.