CSS_Kidd - 4:35 pm on Jan 7, 2010 (gmt 0)

I hope I can explain this right.

I have a solid blue background color on a web page. Then I have a 800px solid white centered container that is going to hold all my content.

What I want to do is have transparent blue div that while over the white, will be as close to the solid blue page background as I can get it.

Right now I am just eyeballing it. And I would like to know if there is an actual method to figuring this out. I have searched everywhere with no answers.

This is as close as I can get it.
solid blue background = #99ccff
transparent blue over solid white = Opacity 37%, #0099FF

NOTE:
There is no CSS alpha/trans applied. The trans blue is a transparent png image created in illustrator set to 72ppi in RGB color mode (as basic as it gets).

If anyone has a method other than just "eying it", please let me know