function getWindowHeight() {
            var windowHeight = 0;
            if (typeof(window.innerHeight) == 'number') {
                windowHeight = window.innerHeight;
            }
            else {
                if (document.documentElement && document.documentElement.clientHeight) {
                    windowHeight = document.documentElement.clientHeight;
                }
                else {
                    if (document.body && document.body.clientHeight) {
                        windowHeight = document.body.clientHeight;
                    }
                }
            }
            return windowHeight;
        }
        function setFooter() {
            if (document.getElementById) {
                var windowHeight = getWindowHeight();
                if (windowHeight > 0) {
                    var contentHeight = document.getElementById('Madre').offsetHeight;
                    var footerElement = document.getElementById('peu_plana');
                    var footerHeight  = footerElement.offsetHeight;

                    // Depenent del navegador sumo o resto el tamany de la capçalera per tal que el peu es posicioni 
                    // correctament.

                    var browserName=navigator.appName; 
                    if (browserName=="Microsoft Internet Explorer")
                       { windowHeight = windowHeight - 10; }
                    if (browserName=="Netscape")
                       { windowHeight = windowHeight - 62; }


                    if (windowHeight - (contentHeight + footerHeight) >= 0) {
                        footerElement.style.top = (windowHeight - (contentHeight + footerHeight)) + 'px';
                    }
                    else {
                        footerElement.style.top = '0px';
                    }
                }
            }
        }
        window.onload = function() {
            setFooter();
        }
        window.onresize = function() {
            setFooter();
        }