There is a way to do this without an extension in firefox to:
make a bookmark with the link below (same as for opera)
http://shoutbox.menthix.net/basicsearch.php?do=search&keywords=%s
Now go to manage bookmarks, rightclick, properties, and then enter any letter in the keyword-box (for example m). Now you can search with the string
"m <search>" (remove the quotes) in the adress bar