I want to lay out a website with html5 semantic markup. I'm wondering; if I use html5 and style the sections like I do with html4, will it still render properly? I don't want to use really up-to-date html5 stuff like canvas, I just want to future proof this site.
You can do this by using HTML5 Boilerplate.
It comes with Modernizr (which includes html5shiv), and a lot more as well.