I wanted Firefox to take what I put into the search bar and make it lowercase before sending it to the search engine.
I do this because one of the search engines I point to is case-sensitive, although all of the queries I send will only return a value if the query is all lower-case. It's an odd database system, but unfortunately I don't have admin access to modify it myself.
Note that I am using Firefox 2, but this should also be applicable to FF3. I'll update if the instructions are too different.
I did accomplished this by modifying the following chrome component:
file: <APPLICATION FOLDER>\chrome\browser.jar\content\browser\search\ search.xml
*NOTE: Replace "<APPLICATION FOLDER>" with the path to Firefox's installation.
method: handleSearchCommand
change from: [var textValue = textBox.value;]
change to: [var textValue = textBox.value.toLowerCase();]
Let me know if you have any feedback... I just wanted to share this since I found it useful.