code: function() {
          if (this.useIFrame === true) {
              if (!this.frame.childNodes.length) {
                  var eventPane = document.createElement("div"),
                      style = eventPane.style;
                  style.position = "absolute";
                  style.width = "100%";
                  style.height = "100%";
                  style.zIndex = 1;
                  style.backgroundImage = "url(" + this.blankImageUrl + ")";
                  this.frame.appendChild(eventPane);
              }
  
              var id = this.id + '_iFrame', iframe;
              if (parseFloat(navigator.appVersion.split("MSIE")[1]) < 9) {
                  // Older IE versions do not set the name attribute of an iFrame 
                  // properly via DOM manipulation, so we need to do it on our own with
                  // this hack.
                  iframe = document.createElement('<iframe name="'+id+'">');
  
                  // IFrames in older IE versions are not transparent, if you set
                  // the backgroundColor transparent. This is a workaround to get 
                  // transparent iframes.
                  iframe.style.backgroundColor = '#FFFFFF';
                  iframe.style.filter          = 'chroma(color=#FFFFFF)';
              }
              else {
                  iframe = document.createElement('iframe');
                  iframe.style.backgroundColor = 'transparent';
  
                  // iframe.name needs to be an unique id, otherwise it 
                  // could happen that other iframes are overwritten.
                  iframe.name = id;
              }
  
              // some special properties to avoid scaling the images and scrollbars 
              // in the iframe
              iframe.scrolling      = 'no';
              iframe.marginWidth    = '0px';
              iframe.marginHeight   = '0px';
              iframe.frameBorder    = '0';
  
              iframe.style.position = "absolute";
              iframe.style.width    = "100%";
              iframe.style.height   = "100%";
  
              if (this.layer.opacity < 1) {
                  OpenLayers.Util.modifyDOMElement(iframe, null, null, null,
                      null, null, null, this.layer.opacity);
              }
              this.frame.appendChild(iframe);
              this.imgDiv = iframe;
              return iframe;
          } else {
              return OpenLayers.Tile.Image.prototype.getImage.apply(this, arguments);
          }
      }
docs: Method: getImage
  Creates the content for the frame on the tile.