onkeypress 和 onkeydown 是有区别，下面将讲解 onkeypress 与 onkeydown 事件的区别。 
onkeypress 事件在用户按下并放开任何字母数字键时发生。但是系统按钮（例如：箭头键、功能键）无法得到识别。 
onkeydown 事件在用户按下任何键盘键（包括系统按钮）时发生。 
具体区别： 
1. 一个放开一个没有放开，onkeydown 先于 onkeypress 发生。 
2.onkeypress 无法系统按钮。 
2.onkeydown 捕获的 keyCode 不区分字母大小，而 onkeypress 区分。

onkeypress是在用户按下并放开任何字母数字键时发生。系统按钮（例如，箭头键和功能键）无法得到识别。 
onkeyup 是在用户放开任何先前按下的键盘键时发生。 
onkeydown 是在用户按下任何键盘键（包括系统按钮，如箭头键和功能键）时发生。

onkeypress 
As of Microsoft® Internet Explorer 4.0, the onkeypress event fires and can be canceled for the following keys:

Letters: A - Z (uppercase and lowercase) 
Numerals: 0 - 9 
Symbols: ! @ # $ % ^ & * ( ) _ - + = < [ ] { } , . / ? \ | ' ` " ~ 
System: ESC, SPACEBAR, ENTER

onkeydown 
As of Microsoft® Internet Explorer 4.0, the onkeydown event fires for the following keys:

Editing: DELETE, INSERT 
Function: F1 - F12 
Letters: A - Z (uppercase and lowercase) 
Navigation: HOME, END, LEFT ARROW, RIGHT ARROW, UP ARROW, DOWN ARROW 
Numerals: 0 - 9 
Symbols: ! @ # $ % ^ & * ( ) _ - + = < [ ] { } , . / ? \ | ' ` " ~ 
System: ESC, SPACEBAR, SHIFT, TAB

As of Internet Explorer 5, the event also fires for the following keys:

Editing: BACKSPACE 
Navigation: PAGE UP, PAGE DOWN 
System: SHIFT+TAB

As of Internet Explorer 5, this event can be canceled for the following keys and key combinations by specifying event.returnValue=false:

Editing: BACKSPACE, DELETE 
Letters: A - Z (uppercase and lowercase) 
Navigation: PAGE UP, PAGE DOWN, END, HOME, LEFT ARROW, RIGHT ARROW, UP ARROW, DOWN ARROW 
Numerals: 0 - 9 
Symbols: ! @ # $ % ^ & * ( ) _ - + = < [ ] { } , . / ? \ | ' ` " ~ 
System: SPACEBAR, ESC, TAB, SHIFT+TAB

You can cancel all keys that fire the onkeydown event in HTML Applications, including most accelerator keys, such as ALT+F4.

In Internet Explorer 4.0, you cannot cancel the onkeydown event, but you can use the onkeypress event to cancel keyboard events.

两个一起按，可以这样：

if( window.event.shiftKey && event.keyCode==xx) function document_onpress()
{ if(event.keyCode=='13')
{
document.all.div_Line.style.pixelLeft=document.all.div_Line.style.pixelLeft+1;
document.all.div_Q.style.pixelLeft=document.all.div_Q.style.pixelLeft+1;
document.all.div_T.style.pixelLeft=document.all.div_T.style.pixelLeft+1; }