function slidecontent(a,b){
  var contentWidth = a*160;
  content = document.getElementById("scrollcontent");
  var currMargin = parseInt(content.style.marginLeft);
  var newMargin = currMargin+b;
  if(newMargin<=0 && newMargin>=-contentWidth+640){
    content.style.marginLeft = (newMargin) + "px";
  }
}