留作自用
document.oncontextmenu = null;
enableSelection(document.body);
function enableSelection(target) {
if (typeof target.onselectstart != "undefined")
// IE
target.onselectstart = null;
else if (typeof target.style.MozUserSelect != "undefined")
// Firefox
target.style.MozUserSelect = "";
else
{
target.onmousedown = null;
target.onmouseup = null;
}
target.style.cursor = "";
}