document.oncontextmenu = function() { return false; }
// IE
document.onselectstart = function()
{
    if (event.srcElement.type != "text" && event.srcElement.type != "textarea" && event.srcElement.type != "password")
    {
        return false;
    }
    else
    { 
        return true;
    }
};
// FireFox
if (window.sidebar)
{
    document.onmousedown = function(e)
    {
        var obj=e.target;
        if (obj.tagName.toUpperCase() == "INPUT" || obj.tagName.toUpperCase() == "TEXTAREA" || obj.tagName.toUpperCase() == "PASSWORD")
        {
            return true;
        }
        else
        {
            return false;
        }
    }
}