If that does not work, check the Help menu. Check your text links. If you use frames on your page, make sure that each frame has a title. If it doesn't, provide the information in another format. At its most basic, that means relying using heading tags, and not font sizes to change the relative appearance of text.
Many users have visual impairments and learning disabilities.
So, minimize or avoid flashy graphics that can confuse and odd color combinations that lack contrast. You can use the On-line Version to check one page, or you can Download the Bobby program to check an entire site. You can also get Help using Bobby. If you're site gets Bobby Approval, you can put their Bobby icon on your site for all to see. In a perfect world, accessibility would be a given.