Zero border between two content panels

[Bing Qiao]

var innerLayout = new Ext.BorderLayout('innerLayout', {
north: {initialSize: 50, margins: {top: 0, left: 0, right:0, bottom: 0}},
center: {margins: {top: 0, left: 0, right:0, bottom: 0}}
});
innerLayout.add('north', new Ext.ContentPanel("innernorth", {content: 'test'}));
innerLayout.add('center', dialogPanel);
var nestedLayout = new Ext.NestedLayoutPanel(innerLayout);
How can I set the border of both content panels to zero so that the two look like one panel?

Thanks very much!

[Bing Qiao]

innerLayout.regions.north.getEl().setStyle('border', '0px');