Question

I have tried everything, but without javascript I cannot achieve the bad layout my designer gave to me!!

As you can see I have the div #backgr-box that has to be absolute positioned with z-index to be properly behind the #contenuto (which holds the page content!!)
Now to solve the extensibilty trouble of #backgr-box I have the below code that works if the content of #contenuto is longer than the sidebar #barra-laterale , but it is not ok in opposite case, see page: http://demo.liquidfactory.it/secondopolo/per-informarti

So how can I tell javascript to apply that calculation only over a minimum height of div sidebar #barra-laterale ??

Need help.. please!

function equalHeight(group) {
           tallest = 0;
           group.each(function() {
              thisHeight = $(this).height();
              if(thisHeight > tallest) {
                 tallest = thisHeight = $("#contenuto").height() - 380;
              }
           });
           group.height(tallest);
        }
        $(document).ready(function() {
           equalHeight($(".column"));
        });

Answer 1

The problem is likely with this line:

tallest = thisHeight = $("#contenuto").height() - 380;

Currently it is setting both the variables tallest and thisHeight to the height of the content region minus 380 pixels. Change it to:

tallest = thisHeight;

And it will resize all the columns to the height of the tallest one.

Edit: It looks like your right-hand column actually consists of multiple columns with a class of .barra-laterale in this case you may want to take another tack altogether:

// calculate the total height of the content are and sidebar
var contentHeight = $("#contenuto").height();
var sidebarHeight = 0;
$(".barra-laterale").each(function() { sidebarHeight += $(this).height(); })

if (sidebarHeight > contentHeight) {
    $("#contenuto").height(sidebarHeight);
} else {
    // extend the last sidebar column to cover the difference between the 
    // height of the content and the sum of the sidebar heights
    var lastSideBarHeight = $(".barra-laterale").last().height();
    var heightDifference = contentHeight - sidebarHeight; 
    $(".barra-laterale").last().height(lastSideBarHeight + heightDifference) 
}