function setClass(myElement) {
    if ( UA_BROWSER == "MSIE")
        myElement.className = myElement.getAttribute("class") + " " + CLASSES.join(" ");
    else 
        myElement.setAttribute("class", myElement.getAttribute("class") + " " + CLASSES.join(" "));
}


if (screen.width <= 800)
    var UA_SIZE = "small";
else if (screen.width >= 1280)
    var UA_SIZE = "big" ;
else
    var UA_SIZE = "medium";

var CLASSES = new Array( UA_OS, UA_BROWSER, UA_SIZE, UA_VERSION);

setClass(document.getElementsByTagName("body")[0]);