There may be a small percentage of visitors with physical disabilities, who have problems in navigating with the mouse. In such conditions, it is better to provide a large display on which visitors can click their choice, instead of providing a very small button on which to click. Try to maintain a standard format on your Website where the choice buttons appear in a specific corner of every page. This will make life easier for all your visitors, including those physically impaired.
If your Website contains videos, then this might pose a problem to those people with hearing disabilities. In such cases, you could attach streaming text at the bottom of your video that runs along with the video or if you regularly change your applets or plug-ins. You could also provide a hyper-link that provides such visitors all text in readable form.