<!DOCTYPE html>
<html>

<head>
<meta charset="UTF-8">
<script>

function test()
{
    document.getElementById("to_msgothic").style.fontFamily = "MS Gothic";
    document.getElementById("from_msgothic").style.fontFamily = "Times";
}

</script>
</head>

<body onload="test();">

<div id="to_msgothic">This should be a yen-sign: \</div>
<div id="from_msgothic" style="font-family: MS Gothic">This should be a backslash: \</div>

</body>

</html>