IBM Corp. on Thursday will preview technology intended to assess and grade Web sites on their accessibility to people who are visually impaired and blind.

A Java-based developer tool called aDesigner is intended to ensure the usefulness of Web pages for people who are visually impaired, IBM said. Developed at IBM’s Tokyo Research Lab, the tool detects accessibility and usability problems on Web pages and provides guidance on how to correct these issues. The issue of easily viewable Web sites is one that will grow, with seven in 10 Americans expected to work past the once-typical retirement age of 65, IBM stressed.

IBM’s aDesigner “presents a console to the developer and it basically provides it as a simulator,” said Jim Chao, emerging technology strategist at IBM. “It simulates a low-vision mode and it also simulates a blind mode so it will take a look at your HTML and in this console list all the problems with your Web page.”

For those who are visually impaired, elements are checked such as font sizes, contrast between foreground and background, and inappropriate color combinations. For people who are blind, aDesigner checks the HTML tags that link to the text-to-speech systems used by those who are blind. The tool checks excessive reaching time, which is the amount of time needed to reach each element of a page, as well as redundant text, insufficient intra-page linking, and accessibility guidelines.

As an alphaWorks project, aDesigner is in the early adopter stage, Chao said. It may be a couple of years before the technology is introduced in an IBM product, he said.

The tool can be downloaded at http://www.alphaworks.ibm.com.