I would start with breaking the projects into functional parts.
- You have the part of sending data from max to server,
- and than the server shall modify a web page.
I remember that people often refer to FLOSC which is a Gateway that allows a flash application to send and receive OSC data. That might be good start.
Do you mean change an image of the website, or change the way the site appears to anyone who looks at it in a browser?
If the second, Jan’s suggestions are best.
If the first, the solution is much simpler: use jit.desktop to capture an image of the site in your browser, then modify with jit.hue or au.hue (Auvi object) or whatever processing you like. Probably you would need two monitors, one for the browser and one to display your effected image.