I've written scripts to filter out threads and posts in a programming forum by author.
But you need to post the code into the web console for each page individually.
I was wondering if it were possible and if so how (using either firefox or chrome), to set your browser up to run a specific script upon loading a specific site? Is it possible as an extension or plugin?
You can use Tampermonkey for Google Chrome
Tampermonkey is the most popular userscript manager for Google Chrome.
Greasemonkey for Firefox:
Allows you to customize the way a web page displays or behaves, by using small bits of JavaScript.