Use wrapper methods/classes for each of those HTML5 specific features. Initially, probably for most of the early adopter phase you can get away with using/expec

Use wrapper methods/classes for each of those HTML5 specific features. Initially, probably for most of the early adopter phase you can get away with using/expecting the HTML5 feature to be present. When you do need to support browsers that don't support or brokenly support those features, you can add in support at the wrapper level without having to do any serious refactoring. Also, keep a careful eye on the HTML5 draft recommendations, just in case features change their implementations. It's unlikely for a feature supported in two independent modern browsers to change unless there's a fundamental problem, or patent workaround needed.