code: function(lod) {
          // the max extent we're provided with just overlaps some tiles
          // our real extent is the bounds of all the tiles we touch
  
          var numTileCols = (lod.endTileCol - lod.startTileCol) + 1;
          var numTileRows = (lod.endTileRow - lod.startTileRow) + 1;        
  
          var minX = this.tileOrigin.lon + (lod.startTileCol * this.tileSize.w * lod.resolution);
          var maxX = minX + (numTileCols * this.tileSize.w * lod.resolution);
  
          var maxY = this.tileOrigin.lat - (lod.startTileRow * this.tileSize.h * lod.resolution);
          var minY = maxY - (numTileRows * this.tileSize.h * lod.resolution);
          return new OpenLayers.Bounds(minX, minY, maxX, maxY);
     }
docs: Method: calculateMaxExtentWithLOD
  Given a Level of Detail object from the server, this function
  calculates the actual max extent
  
  Parameters:
  lod - {Object} a Level of Detail Object from the server capabilities object
  representing a particular zoom level
  
  Returns:
  {<OpenLayers.Bounds>} The actual extent of the tiles for the given zoom level