if (navigator.appName.charAt(0) == 'N') {
	window.document.onkeydown = protectKey;
}
else if (navigator.appName.charAt(0) == 'M')
{
	window.document.onkeydown = protectKey2;
}

	function protectKey(event)
	{               
        // F5
        if(event.keyCode == 116) { return false;}
        // CTRL+R
        else if ((event.keyCode == 82) && (event.ctrlKey == true)) { return false;}
        // CTRL+N
        else if ((event.keyCode == 78) && (event.ctrlKey == true)) { return false;}
		// CTRL+B
		else if ((event.keyCode == 66) && (event.ctrlKey == true)) { return false;}
	}

	function protectKey2()
	{               
        // F5
        if(event.keyCode == 116)
        {
			event.keyCode = 0;
			return false;
        }
        // CTRL+R
        else if ((event.keyCode == 82) && (event.ctrlKey == true))
        {
			event.keyCode = 0;
			return false;
        }
        // CTRL+N
        else if ((event.keyCode == 78) && (event.ctrlKey == true))
        {
			event.keyCode = 0; 
			return false;
        }
		// CTRL+B
		else if ((event.keyCode == 66) && (event.ctrlKey == true))
        {
			event.keyCode = 0; 
			return false;
        }
	}