function clickButton(e, buttonid)
{
    var bt = document.getElementById(buttonid);
    if (typeof bt == 'object')
    {
        try 
        {
            if(navigator.appName.indexOf("Netscape")>(-1))
            {
                if (e.keyCode == 13)
                {
                    bt.click();
                    return false;
                }
            }
            if (navigator.appName.indexOf("Microsoft Internet Explorer")>(-1))
            {
                if (event.keyCode == 13)
                {
                    bt.click();
                    return false;
                }
            }
        } 
        catch (er) 
        {
            // invoke the default postback handler for buttons that render as tags
            __doPostBack(buttonid,'');
        }
    }
}