One of the most useful Firefox tips I have come across is the ability to paste lines of text that include newlines into the address bar and have it automatically account for the new lines.  This has come in quite handy recently while perusing some of my apache logs.  It’s pretty simple too:

1. Type

   1	about:config

   into the address bar
2. Look for the preference name

   1	editor.singleLine.pasteNewlines

   or just type

   1

   paste

   into the filter
3. Double-click that setting and change it from 1 to however many lines you think you’ll tend to paste in - I used

   1

   3

Can you can copy and paste multi-line URL’s!