var intervalID;
//var max=514;
var max=481;
//var min=33; 
var min=0; 
var delta=25;             

function plus(delta) {
  var nWidth = document.getElementById("div_slide_block").offsetWidth;
  nWidth = parseInt(nWidth);
  nWidth +=delta;  
  if (nWidth<=max)
  { 
    document.getElementById("div_slide_block").style.width = nWidth + "px";
  }
  else  {
         if (nWidth==max) window.clearInterval(intervalID);
         else plus(delta-1);
        }
}

function minus(delta) {
  var nWidth = document.getElementById("div_slide_block").offsetWidth;
  nWidth = parseInt(nWidth);
  nWidth = nWidth - delta; 
  if (nWidth>=min)
  { 
    document.getElementById("div_slide_block").style.width = nWidth + "px";
  }
  else {
          if (nWidth==min) window.clearInterval(intervalID);
          else minus(delta-1);
       }
}

function slideOn() {
if (intervalID) window.clearInterval(intervalID);

    intervalID = window.setInterval("plus("+delta+")", 1);
    
}
function slideOff() {
if (intervalID) window.clearInterval(intervalID); 
intervalID = window.setInterval("minus("+delta+")", 1);

}