FitText makes font-sizes flexible. Use this plugin script on your fluid or responsive layout to achieve scalable headlines that fill the width of a parent element.
If you have a small site and don't want to attach jQuery, just attach fittext.js and put this just before (responsive_headline is an header id).
<script>
window.fitText( document.getElementById("responsive_headline") );
</script>
The default setting works pretty well, but when it doesn't FitText has one setting you can adjust. If your text resizes poorly or is resizing all hurdy gurdy, you'll want to turn tweak up/down the compressor. It works a little like a guitar amp.
window.fitText( document.getElementById("responsive_headline"), 1.2 ); // turn the compressor up (font will shrink a bit more aggressively)
window.fitText( document.getElementById("responsive_headline"), 0.8 ); // turn the compressor down (font will shrink less aggressively)
This will hopefully give you a level of "control" that might not be pixel perfect, but scales smoothly & nicely.
Thanks to Trent, Dave and Reagan for original FitText.js: https://github.com/davatron5000/FitText.js http://fittextjs.com/