OpenLayers.Layer.PointGrid and bounds

Question

I'm trying to set bounds for PointGrid. I have map object which is 500x1500, but it's not working.

Code:

 var points = new OpenLayers.Layer.PointGrid({
                name        : "Points grid",
                dx          : 25,
                dy          : 25,
                maxFeatures : 4000,
                ratio       : 1,
                gridBounds  :  OpenLayers.Bounds.fromArray([0, 0, 500, 1500]),
                origin      : new OpenLayers.LonLat(0, 4),
                styleMap: new OpenLayers.StyleMap({
                    pointRadius: 1,
                    strokeColor: "#895656",
                    strokeWidth: 0,
                    fillOpacity: 1,
                    fillColor: "#EFAFAF",
                    graphicName: "square"
                })
            });