How to get html to print return value of javascript function?

What is the preferred syntax to get html to print return value of javascript function?

function produceMessage(){
    var msg= 'Hello<br />';
    return msg;
}

EDIT: Yikes, too many answers without me clarifying what I meant. I know how to do it via the script tag. However, let's say I wanted to make the message red. Would I just encase the script tag inside my css like so?

<div style="color:red><script>document.write(produceMessage())</script></div>

I guess my main question was, should you be using document.write to get the return values to print?