The default latex math symbol for v looks like a nu. I usually use \varv to avoid that stupid letter. However, MathJax does not support \varv. Here's what I did for my wordpress site www.cfdmath.com. In my header scripts (or where ever you put your mathjax script) add the following:
<script type="text/x-mathjax-config">According to MathJax documentation, this essentially enforces MathJax to use web-based or image fonts. It seems to do the trick and all my v's look pretty now.
MathJax.Hub.Config({
"HTML-CSS": {
availableFonts: []
}
});
</script>