code: function(url, size, offset, calculateOffset) {
          this.url = url;
          this.size = size || {w: 20, h: 20};
          this.offset = offset || {x: -(this.size.w/2), y: -(this.size.h/2)};
          this.calculateOffset = calculateOffset;
  
          var id = OpenLayers.Util.createUniqueID("OL_Icon_");
          this.imageDiv = OpenLayers.Util.createAlphaImageDiv(id);
      }
docs: Constructor: OpenLayers.Icon
  Creates an icon, which is an image tag in a div.
  
  url - {String}
  size - {<OpenLayers.Size>|Object} An OpenLayers.Size or an
  object with a 'w' and 'h'
  properties.
  offset - {<OpenLayers.Pixel>|Object} An OpenLayers.Pixel or an
  object with a 'x' and 'y'
  properties.
  calculateOffset - {Function}