can i load local CSS file when loading a specific webpage from the internet?

Question

my question is pretty much direct.

i just want to customize the css of a site that im accessing from my local PC(currently using firebug to change it temporarily).

i want to load an extra css file for that website(only on my PC).

i been wondering about this for long, do you have any idea how can this be achieved?

for example if the site has a code:

body{
   background:blue;
}

i want it to use:

body{
   background:red !important;
}

every-time i load that website.

Answer 1

If you have Google Chrome or Mozilla Firefox, then you can use Stylish. It's an extension for both. It may be under the name 'UserStyles' as well. It's relatively simple to use; you just need to install it and add in your personal styles.
Chrome Version
Firefox Version

Answer 2

Use an extensions like stylish or userscript/greasemonkey

Answer 3

You should be able to accomplish something like this with a browser extension. Search for 'browser extension' along with the browser you want to implement it for.