If you are attaching any documents to your site, whether PDF files, Microsoft Word, PowerPoint, etc., you should ensure that they have been run through the Accessibility checkers provided you by the newer versions of MS Office products. To find their checkers, search through each product as their locations may vary with versions.
Non-HTML Content/Documents
When possible, stick to using PDFs as not all people will have the Office suite of applications, especially on their mobile phones.