Looking for a hotkey program that works with firefox?

Looking for a free hotkey program that works with firefox? Basically something that I can assign strings of text to be pasted when I press Ctrl+ whatever letter. There is Polyphony Keyboard manager but I don't want to spend any money. Looking for something similar to that. Any suggestions? Thanks.

You can do this with Autofill Forms Firefox Add-on

Pretty sure the imacros addon for Firefox is free as well. Just Google 'firefox macro addon' or 'firefox macro plugin' or something.