Im making a responsive design, which has to keep the proportions of its elements (height to width) no matter what the screen size is, so i don't know the size in pixels for any of the elements and i can work only in %.
I can set either the width or the height as a % of the browser size, but the i have no idea how to set the other property value.
That using only CSS, making JS calculate the values is not an option.
I came across this problem last year and found an obscure solution after some tedious researching. Unfortunately it involves wrapper DIVs. The structure is simple - you have a parent DIV which contains the contents container and another DIV that sets the proportions. You set the margin-top of the 'proportion' DIV as percent of the width of the parent... Example:
#parent {
position: relative;
}
.proportions {
margin-top: 75%; /* makes parent height to 75% of it's width (4:3) */
}
.container { /* contents container with 100% width and height of #parent */
position: absolute;
top: 0px;
left: 0px;
bottom: 0px;
right: 0px;
}