Flash pop up ads

i know we all hate pop ups but i also know some of you guys have seen those flash ads that pop up over the HTML and have a clear background. i know of the tutorial on here that shows you how to give flash files a clear background.

I want to know how to:
a) make this cross browser compatable
b) make the flash file appear over the HTML (like those ads you’ve seen where the animation moves across the page over all the text)

thanks =)

try http://www.macromedia.com/support/flash/ts/documents/wmode.htm

hope it helps

you have to use layers and eventually wmode if you must