Gmail has a seemingly simple but actually powerful filtering system. The "Has the words" input field can be used for arbitrary  queries . However, the one line input is very cramped when trying to filter multiple mailing lists at once. A textarea would be more appropriate.  Initially, this seemed like a job for Greasemonkey . However, since the filter input form is created dynamically, it's hard to detect when it's visible without resorting to polling. Instead, it seemed easier to find the right node with a CSS selector like  input[name="cf1_has"] . Then, XBL  can be used to replace the input node with a textarea node (styled appropriately). All that's really necessary is to insert the following in  userContent.css : @-moz-document domain( mail.google.com ) {   input[name="cf1_has"] {     display: none;     -moz-binding: url( http://persistent.info/files/gmail-filter.xml#filter );   } }  The XBL file  is pretty straightforward (it didn't ...