function KeyDown()
{
    //屏蔽鼠標右鍵、Ctrl+n、shift+F10、F5刷新、退格鍵
    //alert("ASCII代碼是："+event.keyCode);
    
    // Block Alt + <- ->
    if ((window.event.altKey)&&((window.event.keyCode==37) || (window.event.keyCode==39)))
    {
        alert("Can't use Alt + <- ->");
        event.returnValue=false;
    }
    
    
    // Block Backspace unless TextEdit and other
    if (event.keyCode == 8)
    {
        var objSource = window.event.srcElement;
        if (objSource.isTextEdit)
        {
            if ( (objSource.readOnly) || (objSource.type == "submit") || (objSource.type == "button") || (objSource.tagName=="BODY") )
            {
                event.returnValue = false;
            }
        }
        
        else
        {
            event.returnValue = false;
        }
        
        //event.keyCode = 0;
        //event.returnValue = false;
    }
    
    // Block F5 F1 Ctrl-R
    if ((event.keyCode==116) || (event.keyCode==112) || (event.ctrlKey && event.keyCode==82))
    { 
        event.keyCode=0;
        event.returnValue=false;
    }
    
    // Block Ctrl-N
    if ((event.ctrlKey)&&(event.keyCode==78))
        event.returnValue=false;
    
    // Block Shift-F10
    if ((event.shiftKey)&&(event.keyCode==121))
        event.returnValue=false;
    
    // Block Shift-Leftbutton
    if (window.event.srcElement.tagName == "A" && window.event.shiftKey)
        window.event.returnValue = false;  
    
    // Block Alt-F4
    if ((window.event.altKey) && (window.event.keyCode==115))
    { 
        window.showModelessDialog("about:blank","","dialogWidth:1px;dialogheight:1px");
        return false;
    }
}

function Showhelp()
{
    alert("You press F1");
    return false;
}