The different browser models handle dragging and dropping very differently, and it's quite complicated in any case (involves reading the position of the mouse from the event, re-setting the absolute position of the element each time this changes etc.).
I would suggest you're far better off using a library that covers this for you. jQuery is extremely popular. They have "draggables" and "dropables" plugins:
http://docs.jquery.com/UI - although I have never used them and there doesn't seem to be a tutorial.
If you're quite comfortable with OO principles within JavaScript you might try the mooTools drag object:
http://docs.mootools.net/Drag/Drag-Base.js
Other libraries that might have stuff you want to look at:
Dojo:
http://dojotoolkit.org/book/dojo-book-0 ... g-and-drop
Ext 2.0:
http://extjs.com/learn/Tutorial:Custom_ ... rop_Part_1
Let me know how you get on as I've never used any of these, and someday I'm sure I'll want to do some of this and want to know what the best tools are.
Ta,
Robin.
