If you use outside resources for your web needs, or have a dedicated web person or company, call them immediately. If you have a department or staff, even better. But— if you are working on your own, you would do yourself and your business a favor to contact a reputable web developer to discuss how to make your site accessible and avoid possible lawsuits. The older your website, the more likely it is that it is NOT compliant. Take action now!
Web designers often design in such a way that does not allow the user to adjust font size or color. While they may be protecting their brand, they are also inhibiting some users. Many visually impaired need to use high contrast color settings or very large fonts to read a website. Don't design your website in a way that makes it impossible for them to do this.
Courts have essentially taken three positions when approached with this issue. Some courts take the position that the ADA applies to all commercial sites because the law was meant to protect disabled individuals from having a more difficult time than able-bodied individuals from doing business. That is why the website Scribd was unable to get a case summarily dismissed and ended up settling.