GWT DockLayoutPanel

DockLayoutPanel dlp = new DockLayoutPanel(Unit.EM);
dlp.addNorth(new HTML("header"), 2);
dlp.addSouth(new HTML("footer"), 2);
dlp.addWest(new HTML("navigation"), 10);
dlp.add(new HTML("HTML Contents"));

Do not mention center panel size, the remaining space will be allocated to the center panel.