code: function (px) {
          //if no px passed in, use stored location
          if (px != null) {
              this.px = px;
          }
  
          if (this.imageDiv != null) {
              if (this.px == null) {
                  this.display(false);
              } else {
                  if (this.calculateOffset) {
                      this.offset = this.calculateOffset(this.size);  
                  }
                  OpenLayers.Util.modifyAlphaImageDiv(this.imageDiv, null, {
                      x: this.px.x + this.offset.x,
                      y: this.px.y + this.offset.y
                  });
              }
          }
      }
docs: Method: moveTo
  move icon to passed in px.
  
  Parameters:
  px - {<OpenLayers.Pixel>|Object} the pixel position to move to.
  An OpenLayers.Pixel or an object with a 'x' and 'y' properties.