if (typeof(element.onselectstart) != "undefined") {        
    // IE下禁止元素被选取        
    element.onselectstart = new Function("return false");        
} else {
    // firefox下禁止元素被选取的变通办法        
    element.onmousedown = new Function("return false");        
    element.onmouseup = new Function("return true");        
}