I advise that they should install the most recent version of the style pack, which is UBBT77.zip. The ones prior to that are barely maintained, but did get a major update in 2015 to handle some showstopping issues with mobile, and to update poorly formatted css (what you're /probably/ pointing out now), and fix some css errors.
Again, updating their website files is all the job of the technically inclined forum owner (web administrator) to undertake. Point them to that post. They should be able to read it and easily understand it.
