There are countless resources available on accessible web design.  Listed below are some tools that you can use to check the design of web pages.  There are probably others not listed that are just as good, perhaps better.  Those listed below are fairly representative of what is available.

When you look at resources on accessible web design, always check for references to the Web Accessibility Initiative (WAI) guidelines.

Note: In the final resource, links will open in a new window.

Evaluating Web Sites for Accessibility

W3C Web Accessibility Initiative

http://www.w3.org/WAI/eval/

This article discusses techniques and tools for preliminary review and conformance evaluation of accessibility of web pages, against the international standards, Web Content Accessibility Guidelines 1.0.

Bobby

http://bobby.watchfire.com/bobby/html/en/index.jsp

Bobby offers an online check of websites against the Web Content Accessibility Guidelines.  Enter the URL for the page to generate a report.

According to the Bobby website:

Once your website reaches a Bobby Approved rating, you are entitled (though not required) to use the applicable Bobby Approved icon on your site. These icons identify your organization as one committed to inclusion.

UW-Madison Web Accessibility Checklist

http://helpdesk.wisc.edu/accessibility/checklist.php

Use this checklist online to manually evaluate a website.  The checklist then prepares a summary for you.

A-Prompt

WebAIM

http://aprompt.snow.utoronto.ca/

A-Prompt is software available for free download.  It not only checks pages for accessibility, but provides guidance regarding fixing problems.

Lynx Viewer (Text based browser)

http://www.delorie.com/web/lynxview.html

Lynx is a text-based browser.  You can check your pages to assess how accessible the content is by text only.  The options are to send the URL of the web page for an automated report, or to download Lynx and view the pages yourself as text-based presentations.