Formula for images by screen resolution?

Question

I have 4 images that are of decreasing size down the screen. The composition of these images and their relation to each other must appear the same on all possible screen resolutions, with specific regards to their size, and their margins. In other words, the height, width and margins must all be factors of the height and width of the screen. What is the generic formula if the only known values are the height and width of the screen?
I use the following to get the screen height and width:
string Width = Convert.ToString(HtmlPage.Window.Eval("screen.width"));
string Height = Convert.ToString(HtmlPage.Window.Eval("screen.height"));