To digress a bit from LibGuides ...
The biggest problem with accessibility is not technical: it's cultural.
Producing HTML that meets basic accessibility tests is not all THAT
difficult. The harder part is setting up a culture where everyone --
everyone! -- who writes content for the web is trained on how to do it
accessibly. A content editor who is clueless about accessibility can
very easily screw up their pages without even knowing they're doing so.
The same applies to developers. Once while reviewing a library site's
code, I came across a chunk of HTML that looked like this (roughly):
I don't know why this was here? It's invisible! Disabling.
<a href="#top" class="hidden">Return to top</a>
An earlier developer had put that in to assist screen reader users in
getting back to the top of the page if they wanted. The "hidden" class
was a correctly written class for hiding content while leaving it
available for screen reader users. But the next person to fill that job
wasn't trained on WHY and took it out again.
If you really want to commit to accessibility, it needs to be a
criterion in the job description for your developers, and there needs to
be a training process in place for anyone who produces content for your
site. Probably with refreshers at intervals.