var panels = new Array('panel1', 'panel2', 'panel3', 'panel4');

function showPanel(tab, panelName)
{
        var panelToShow = document.getElementById(panelName);

        for(i = 0; i< panels.length; i++)
        {
                // Get the current panel
                var curPanel = document.getElementById(panels[i]);
                // If it exists, hide it
                if (curPanel != null)
                        curPanel.style.display = 'none';
                if(panelName=="panel3" && i==2)
                {
                 document.getElementById("test").src="test.php";
                }
        }

        // This line works around a display bug in Gecko-based browsers
        panelToShow.style.display = 'inline';

        // Show the panel
        panelToShow.style.display = 'block';

        return false;
}