alert()statements. It generates a pop-up with whatever you pass in as argument. Another way to do it is by
dump() messages. This function outputs to the terminal. See MDN’s write up about it.
Basically, XUL is XML. XUL files are where you define the layout of the program. Kinda like how HTML does it. Yes, both of them are really similar. Since XUL is a mozilla technology, I would recommend you to go to MDN for help. They have a XUL school and a XUL reference documentation.
A DOM Inspector Calls
You might have heard of firebug or the Chrome browser’s html inspector. The DOM inspector works the same way like them but it is used to inspect both html and XUL. If you are working on layout bugs, you can’t live with it.
When you are working on bugs in open source projects, always remember to RTFM (Read The Friendly Manual). Do get used to the MDN docs when you are working on these two languages. If you are still in doubt, don’t be afraid to ask! You may approach me (:jyeo), the tutors in CP3108 or any of the developers in irc.mozilla.org. Have fun squashing those bugs!