CSS: a grid with 4 requirements

hi,

I need to implement a grid with the following features:

1) the columns width is fixed

2) the columns number depends on the window width

3) the elements has not fixed height

4) the content should be possibly vertically distributed

For now, The first two points are satisfied. I gave up on the 4th one. But I absolutely need to fix the 3rd point.

Please see this image to better understand the problem:

http://dl.dropbox.com/u/72686/grid.png

CSS:

div.item-list { 
    width: 100%; padding: 0; margin: 10px 0;    list-style: none;
}

div.item-list li.views-row {
    float: left; width: 200px; /*Set default width*/ padding: 0; margin: 5px 0; display: block;
}

div.item-list li.views-row  div.node { 
  /* height: 755px;*/ margin-right: 10px; /*Creates the 10px gap between each column*/ padding: 20px; background: #e3e1d5; 
}