I want to understand how web accessibility experts deals with websites if they want to confirm that those sites are compatible with accessibility guidelines. Do they have to understand any server-side language? or just HTML and CSS?
For example, if there is a company website which provides services for other sites to ensure the accessibility for them, do they have to have a look at the server side code or only the output HTML and CSS?
2
Usually just the output. The only server-side issue I can think of now is how to ensure a site has pretty urls like, “/user/logins/all-time” instead of /index.php?item=users&lookup=logins&timeframe=all-time, which is not at the height of accessibility. (usually mod_rewrite magic in an .htaccess file, but so many other ways, too).
But, by far, the most important aspect of accessibility, IMHO, is the content; HTML markup is merely a sub-topic of that.