FoxReplace is a nice little Firefox add-on that you may use to substitute certain words on web pages with something else. It’s as simple as instructing the browser to replace all instances of word "xxx" with "yyy" like in Notepad.
And in case you like to completely hide a word from appearing on web pages, just use a blank instead of specifying a replacement string.
To understand the usage, let’s take this real-world example: Comments written on Digg and YouTube can sometimes leave a normal person depressed because of their language but here’s how FoxReplace can help you.
First create a new rule that applies to all URLs from digg or youtube.com. We use *.youtube.com instead of youtube.com to take care of country specific domains.
Now in the Substitutions panel, choose the "Regular Expression" option and add multiple ‘find & replace’ entries as show in this screenshot.
If you are new to regular expressions, a.*hole will match all words or phrases like a**hole, a**-hole, a** hole, etc. and they will automatically get replaced with the word "awesome".
This is just one example. You may even use Fox Replace to turn Firefox into a slightly more kid-safe browser by specifying a list of stop-words that never appear on web pages.
Or you can use the add-on to edit web pages before capturing not-so-original screenshots.