js禁止页面刷新后退

window.event.returnValue = false; //屏蔽 shift 加鼠标左键新开一网页???????
if ((window.event.altKey)&&(window.event.keyCode==115)) //屏蔽Alt+F4???????
{???????
window.showModelessDialog("about:blank","","dialogWidth:1px;dialogheight:1px");???????
return false;???????
}???????
}???????
</script> <script>? ?????function?KeyDown(){?//屏蔽鼠标右键、Ctrl+n、shift+F10、F5刷新、退格键? ??????//alert("ASCII代码是："+event.keyCode);? ??????if?(?(window.event.altKey)&&? ??????(??(window.event.keyCode==37)||?//屏蔽?Alt+?方向键?←? ?????????(window.event.keyCode==39)?)??){?//屏蔽?Alt+?方向键?→? ??????????alert("不准你使用ALT+方向键前进或后退网页！");? ??????????event.returnValue=false;? ??????} ?????if?((event.keyCode==8)?||?//屏蔽退格删除键? ??????　(event.keyCode==116)||?//屏蔽?F5?刷新键? ?????　　(event.keyCode==112)||?//屏蔽?F1?刷新键? ??????　(event.ctrlKey?&&?event.keyCode==82)){?//Ctrl?+?R? ??????　event.keyCode=0;? ??????　event.returnValue=false;? ????　　　alert("不准你使用快捷！");? ??????}? ?????if?((event.ctrlKey)&&(event.keyCode==78))?//屏蔽?Ctrl+n? ?????{ ???????alert("ctrl?+?n"); ????　　event.returnValue=false;? ?????} ??????if?((event.shiftKey)&&(event.keyCode==121))?//屏蔽?shift+F10? ????????{ ????????　　alert("?shift+F10?"); ????????　　event.returnValue=false;? ?????　　} ??????if?(window.event.srcElement.tagName?==?"A"?&&?window.event.shiftKey)? ??　　　{ ?????　　　window.event.returnValue?=?false;?//屏蔽?shift?加鼠标左键新开一网页? ??　　　} ?????? ??????if?((window.event.altKey)&&(window.event.keyCode==115)){?//屏蔽Alt+F4? ??　　　　alert('Alt+F4'); ??????//window.showModelessDialog("about:blank","","dialogWidth:1px;dialogheight:1px");? ??????return?false; ??}? ????} ??document.onkeydown?=?KeyDown??? ??</script>??