To me, accessibility simply means that something is easy to access from any standpoint. Applying this to the web can take on different meanings.

It can mean that the information displayed on a website is organized in such a manner that navigating to and accessing any information one may desire is simple. For example, having a simple, constant format of pages. Having a search function within the site to quickly find specific information, or having links to relating sections of the site. Anything one can do to make surfing the site an easy and pleasurable experience.

It can also mean that a website should store its information in such a fashion that anyone can access it. For example, formatting a website so that a word reading program can read the descriptions of pictures for the blind or adding subtitles for the deaf. All people have the same right to access the same information and easy accessibility makes that happen.

Accessibility can also take on a larger scale,  interacting with other websites to make your information easier to get to. For example, adding keywords to articles so when someone searches for them on Google, your site may come up higher on the list and become more accessible.

To me, making something accessible is making it available to as many people as possible.