var divStatus = 0; 
var theDiv = document.getElementById("DivNameHere"); 

theDiv.onclick = function() { 
    if (divStatus == 0) { 
          //if "this." doesnt work, try "theDiv." 
          this.style.height = "200"; //new height 
          this.style.width = "150"; //new width 
          divStatus = 1; 
    } 
    if (divStatus == 1) { 
          this.style.height = "100"; //old height 
          this.style.width = "75"; //old width 
          divStatus = 0; 
    } 
}