The vector template hasn't yet this css, please have a look at the starter (or 'dokuwiki' tpl when that is your reference) for example styles. (that is about the file lib/tpl/dokuwiki/css/_diff.css)
(Probably the check for updated css is part of your usual update checks, in that case you can ignore this buzz.)
The latest version of DokuWiki has some diff revisions navigation via dropdowns and forward/backward arrows. (e.g. https://www.dokuwiki.org/dokuwiki?rev=1371065967&do=diff )
The vector template hasn't yet this css, please have a look at the starter (or 'dokuwiki' tpl when that is your reference) for example styles. (that is about the file
lib/tpl/dokuwiki/css/_diff.css)(Probably the check for updated css is part of your usual update checks, in that case you can ignore this buzz.)