.Jpeg is not capable of transparency, only .gif and for all but Internet Explorer, .png has transparency. The next update of IE is supposed to support .png transparency.

Jpeg 2000 supports transparency, however, without browsers that are supporting it, what is the reason to use it. It is interesting, that is all.

Image slicing lets you take advantage of two type of files being reassembled in a web page. Gif images are better at saving crisp line images and are preferred for type and cartoon graphics, logos, etc. And they support transparency of one color.

Generally to gain transparency means increasing file sizes, so if you know what color your background is going to be, making the background of the item you are placing on top has apparent transparency. This apparent transparency was used in another method for print for years because of the then limitations of postscript.

The postscript language was modified with Adobe wanted Illustrator's new found transparency to be able to print postscript. DRAW has it for how long?

DRAW is not my favorite for Web Graphics, a great program which is opimized for making web graphics is PhotoImapct. It isn't an expensive program.

DRAW's first dedication is toward print, but has accomodations for web. There are some web optimization tutorials available at Unleash.com.