Make sure that at the very least your home page works fine on every environment you can reasonably support. If specific pages require technologies not widely supported, state it clearly in the links that lead to them (don't need to use anything obnoxious,
alt texts on links and images might suffice) and in the pages themselves (for instance, adding a small header - that might get hidden when/if you're able to detect that the capabilities are present).
Also try to make sure the pages degrade gracefully when the required technologies are not present/enabled. Even if your visitors are tech-savvy, if something in your page just don't work but there's no indication of what is missing, they might not bother go looking for it (unless they're really interested, which is not something can be assumed). OTOH you don't have to give detailed instructions on how to enable what's missing, just stating what needs to be enabled should be enough for this audience.
Update: I'd like to put more emphasis on the last point with a personal anedocte: as a security-aware user, I always browse with NoScript enabled. When I go to a website that has a video, for instance, one of the things below happens:
- There is a placeholder for the video, and clicking it is enough to unblock it;
- There's a placeholder, but clicking is not enough - there is another domain that needs to be unblocked (usually a CDN), often named appropriatly though inconsistently (dailymotion.com/dmcdn.net, youtube.com/ytimg.com, metacafe.com/mcstatic.com);
height statically set, and sometimes there is no hint the page has a video at all. It can go totally missed;
- The video depends on some random ad server, so unblocking the most obvious domains isn't enough to show it. If I'm really interested I can go on unblocking each remaining domains (in the order of less-to-more shady-looking name), sometimes with the effect of more domains that weren't previously there appearing, until the video works or I give up.
This is just to illustrate some problems that can happen even when you assume a modern browser and a tech-savvy user. You don't need to go out of your way to make sure your site works for every possible configuration out there, but it's important that some fail-safe elements are present even in this case.