Intercept an HTTP request at browser end to alter some html content

Question

I would like to do as follows. What would be the best way? A general answer will also be fine.

I would like to intercept an HTTP request at the client end to alter some

Answer 1

or, you can code a toolbar, or maybe a simple chrome addon, it's really easy but its not C#

you can search for libraries to monitor browsing trough proxy, like this:

http://httpproxynet.codeplex.com/

The same concept used by java in this project: http://www.charlesproxy.com/

sounds intresting, good luck :)