What is your reason for not changing the Operating Sytem settings, if you do not mind me asking ? You could easily change them temporarily and then change them back.

Have you considered setting up separate user accounts on your computers XP Operating System, that may be a solution.

You may be interested in this thread " I would like to make the font sizes on my menu bars, tool bars, and tabs larger. How can I change those font sizes only? "

I do not know if XP allows you to overide hi contrast settings within firefox, for the content of the page I will look later on if no one else answers.

John,

thanks for your comments. The computer is mainly used by a visually impaired person. She doesn't do much web surfing though and doesn't really need a high contrast web browser. If however a colleague wants to help her maintain the machine or quickly wants to look up something on the web for her, then it would be great if it was possible to access web pages "unfiltered", in their regular look and feel, as designed by the web author. In fact, the High Contrast Mode significantly changes the way web pages look, and sometimes screen elements needed for navigation etc. are suppressed or rendered invisible. (This, of course, is often related to poor web design, like graphical buttons or links with the actual label as a background image or without an ALT attribute, but unfortunately, vast parts of the web are not really "accessible", so accessibility will remain an issue for the browser as well.)

Creating a separate user account certainly is an option, especially for shared machines, but it makes it more complicated to quickly jump in and give her a hand. That's why separate user accounts are not really popular here; instead, Opera was installed which does not adhere to the OS setting and therefore grants a neutral view to all web pages.

Actually, when I started investigating on that issue, I was quite surprised that there was no option for this in Firefox, not even in "about:config". After all, Firefox obviously queries the OS for the Contrast setting and then chooses to render the page this or that way, so I thought they certainly implemented a flag or something to change the behavior. It seems however there is no such flag, is there? This distinction seems to be entirely hard-wired.

I am not sure if this is the place for change requests, but if somebody stumbles upon this question, is there any chance to make this setting open to the public? Something like an option "accessibility.useoscontrastsetting" or so? This might also facilitate it to develop an add-on for on-demand switching between the two modes, and web designers could check more easily how their work looks for those with poor eyesight.

Greetings, Bounder of Adventure

See if there is anything at this website that helps you with that issue.
http://www.accessfirefox.org/