An HTML page has an inline block in the HEAD like so:
<style type="text/css">
body {font-size: 1.2em}
</style>
This sets the body font size immediately when the page is loaded.
I want to replace this with something more dynamic but still on the client side.
How can I use JavaScript to set such a style that would be available and visible immediately that the page is rendered? Body.onload is too late. I need an equivalent to this style block, but with JavaScript.