$(document).ready(function(){

	// check screen width on load and window resize
	jQuery.event.add(window, "load", checkWindowSize);
	jQuery.event.add(window, "resize", checkWindowSize);

});

function checkWindowSize() {
    var width = $(window).width(),
    new_class = width > 1920 ? 'wlarge' :
                width > 1600 ? 'w1920' :
                width > 1280 ? 'w1600' :
                width > 1024 ? 'w1280' :
                width < 1024 ? 'wsmall' : '';
    $(document.body).removeClass('wlarge w1920 w1600 w1280 wsmall').addClass(new_class);
}