HTML5 has fantastic new features — one of them is
type="number" attribute for
input tags, which (among other things) restricts the user to only entering numbers (and spawning the number keyboard on mobile phones) and giving a (not always useful) widget that lets you increase/decrease the number. Unfortunately, one piece is missing (at least from most browsers I’ve seen): restricting the input to numbers within the min/max range.
input type="number" tags on your site will have their min/max values enforced.