window.onscroll = function() {
    var scroll = (document.documentElement.scrollTop ||
        document.body.scrollTop);
    if(scroll>237){
   		document.getElementById('pub_left').style.position = 'fixed';
		document.getElementById('pub_left').style.top = 0+'px';
		}
		
	if(scroll<237){
        document.getElementById('pub_left').style.top = 237+'px';
		document.getElementById('pub_left').style.position = 'absolute'; //310
		}
}