<p>This test execCommand("FontSize", ...).  You should see 'small' 'medium' and 'large' below in every increasing font sizes.</p>
<div id="div" contenteditable="true"></div>
<ul id="console"></ul>

<script>
function log(str) {
    var li = document.createElement("li");
    li.appendChild(document.createTextNode(str));
    var console = document.getElementById("console");
    console.appendChild(li);
}

var div = document.getElementById("div");
var sel = window.getSelection();

sel.setPosition(div, 0);

if (document.execCommand("FontSize", false, "pasd"))
    log("Failure: execCommand('FontSize', [Illegal value]) should fail.");

if (!document.execCommand("FontSize", false, "2"))
    log("Failure: execCommand('FontSize', [Legal value]) failed.");

document.execCommand("InsertText", false, "small");    

if (!document.execCommand("FontSize", false, "4"))
    log("Failure: execCommand('FontSize', [Legal value]) failed.");

document.execCommand("InsertText", false, "medium");

if (!document.execCommand("FontSize", false, "6"))
    log("Failure: execCommand('FontSize', [Legal value]) failed.");

document.execCommand("InsertText", false, "large");
</script>