A good start point on accessibility is here http://www.w3.org/WAI/. W3C has released a guideline years ago http://www.w3.org/TR/WCAG10/. And a newer version is under development (for a long time) http://www.w3.org/TR/WCAG20/.

Here is a short version that highlight the most relevant guidelines to Geronimo's Admin Console.

Web accessibility guidelines (short version)
1. Provide equivalent alternatives to auditory and visual content.

• Set meaningful ALT attribute for IMG, APPLET elements.
• Provide equivalent text links if a server-side image map is used.

2. Don't rely on color alone.

• Ensure that all information conveyed with color is also available without color.

3. Use markup and style sheets and do so properly.

• Use style sheets to control layout and presentation.
• Use relative rather than absolute units in markup language attribute values and style sheet property values. e.g., in CSS, use 'em' or percentage lengths rather than 'pt' or 'cm'.

4. Create tables that transform gracefully.

• For data tables, identify row and column headers. e.g., use TD to identify data cells and TH to identify headers.
• Do not use tables for layout unless the table makes sense when linearized. Use css instead.

5. Ensure that pages featuring new technologies transform gracefully.

• Ensure that pages are usable when scripts, applets, or other programmatic objects are turned off or not supported. If this is not possible, provide equivalent information on an alternative accessible page.

6. Provide context and orientation information.

• Title each frame to facilitate frame identification and navigation. e.g., in HTML use the "title" attribute on FRAME elements.
• Associate labels explicitly with their controls. e.g., in HTML use LABEL and its "for" attribute.

7. Make all functionality operable through a keyboard interface.

8. Help users avoid mistakes and make it easy to correct mistakes that do occur.