Nice.
I've been looking around how to make a custom preloader, but I haven't found anything good, and then I take a look at this. Hehe.
Thanks for the tutorial :D
Oh, and I also have a question, does the variable _width work with images? (I mean, if you put something like thisimage._width=10 will it change the image's width?) Because I want to make preloaders using some cool stuff, you know, the one color loading bar looks bad, so I want to make a gradient one in photoshop.