function preventSelection(element){
var preventSelection = false;
function addHandler(element, event, handler){
if (element.attachEvent) 
element.attachEvent('on' + event, handler);
else 
if (element.addEventListener) 
element.addEventListener(event, handler, false);
}
function removeSelection(){
if (window.getSelection) { window.getSelection().removeAllRanges(); }
else if (document.selection && document.selection.clear)
document.selection.clear();
}
function killCtrlA(event){
var event = event || window.event;
var sender = event.target || event.srcElement;
if (sender.tagName.match(/INPUT|TEXTAREA/i))
return;
var key = event.keyCode || event.which;
if (event.ctrlKey && key == 'A'.charCodeAt(0))  // 'A'.charCodeAt(0) можно заменить на 65
{
removeSelection();
if (event.preventDefault) 
event.preventDefault();
else
event.returnValue = false;
}
}
addHandler(element, 'mousemove', function(){
if(preventSelection)
removeSelection();
});
addHandler(element, 'mousedown', function(event){
var event = event || window.event;
var sender = event.target || event.srcElement;
preventSelection = !sender.tagName.match(/INPUT|TEXTAREA/i);
});
addHandler(element, 'mouseup', function(){
if (preventSelection)
removeSelection();
preventSelection = false;
});
addHandler(element, 'keydown', killCtrlA);
addHandler(element, 'keyup', killCtrlA);
}
function clickIE4(){
if (event.button==2){
return false;
}
}
function clickNS4(e){
if (document.layers||document.getElementById&&!document.all){
if (e.which==2||e.which==3){
return false;
}
}
}
if (document.layers){
document.captureEvents(Event.MOUSEDOWN);
document.onmousedown=clickNS4;
}
else if (document.all&&!document.getElementById){
document.onmousedown=clickIE4;
}
document.oncontextmenu=new Function("return false")
preventSelection(document);