One of the great things about design is that it is artistic; there are no "absolutes" in web design. There are numerous ways to do same thing, and a lot of it is opinion and not fact.
You can try floating-width layouts with CSS (just beware text that runs all across the page - it makes it unreadable, so check min-width and max-width). You can also use advertisements (even for your own site). You can re-arrange the design to make the content more engaging. Or your could just let the white-space exist :)
Honestly, I think the latter (just ignoring it) may be the best option. Without knowing your site personally and looking at it, I cannot give you true, specific advise. For example, is the main content div of your site 700px wide? 900px? What are your color schemes? Etc... everything plays in. Everything. However, here are some interesting things to note:
- Just because people have a wide-screen monitor does not mean their browser is full-screen.
- people with widescreen monitors are used to seeing a lot of whitespace
- filling whitespace can actually distract users from the content. There are a lot of minimalist designs that do very well
- this may not affect all of your users (or maybe .
On that last point: your target audience is a huge focus of web design. Google Analytics and Piwik are free analytics tools that give you insight to your users and how your users interact with your site, including browser size. Personally, I have been beta testing GraphUX, and find it easier to use (but it won't be free).
The point is, see (a) who your users are, (b) how they use the site, and (c) how to best deliver the content. Sometimes blank space is bad, sometimes it's good.