How can you tell if you're meeting your primary audience's needs effectively? That's not an easy question to answer. One of the best ways to attempt to answer it is to use focus groups. This involves finding a sample of your target audience, have them use your site and ask about their experience. This option, though infinitely valuable, is usually expensive, time consuming and difficult to implement properly. But we're in luck, there's an easier way to get some of the basic information you're trying to find.
As webmasters, we have access to some very good tracking data. If you analyze your log file properly, you can get a tremendous amount of information about the people who are currently visiting your site. With this information you should be able to answer many questions about your current visitors. What times of day are they visiting? What countries are they visiting from? What browsers and operating systems are they using? What pages are they viewing on your site? How are they reaching your site? What's the first page most of them are seeing? Some of this information may seem anecdotal at first, but this information starts to build the complete profile of your current visitors.
Now the big question... Does your current audience's profile match the profile of your target audience? If they match, then you've done well and things are on track. If they don't match, find out why. It's possible that a small, derivative section of your website is outperforming the rest and is skewing your user profile somewhat. This isn't a bad thing though. Take an opportunity like this to explore whether or not this audience can benefit you in any way and do what you have to in order to serve them best. If there's no real reason why your current audience and your target audience don't match, you'll have to go back to the drawing board. Something is off. Either you're not reaching your primary audience with your site and you need to put some work into fixing that problem or, you've misjudged your primary audience's profile and need to re-adjust your perception of who your primary audience is.
It any case, what you need to take away from this is how your current audience compares to your primary audience. Where you go from there is up to you, but learn as much as you can about your current audience to help you make informed decisions.