Editing Help:User style (section)

=== CSS in user subpages versus CSS in a local file ===
In addition to the above, or alternatively, a local CSS can be set on the browser. If one uses multiple browsers, each can be set to a different CSS. Each applies to the whole World Wide Web, not just a MediaWiki project (and does not depend on being logged in). However, a setting only affects other webpages if they use the same CSS selector; e.g. a setting for the selector a.extiw affects fewer pages on the web than one for h2 (but it affects at least all MediaWiki projects, not just one).

For lines of CSS which should be different on different MediaWiki projects, e.g. for a different background color for easy distinction, clearly the local CSS cannot be used; at least these lines should be put in the user subpages.

Some computers, e.g. in internet cafes, mobile devices/tablets, do not allow users to set preferences for the browser. In that case the user subpages allow the setting of a user style anyway.

When the browser has been set to the option to ignore the font size specified in the webpage or external CSS, CSS lines regarding font size have to be put in the local CSS.