Do you know how to check the standing of your website and the traffic that it's bringing in?

I just signed on a new web design client and for the umpteenth time learned that, like so many entrepreneurs, she has no idea whether her existing website is performing well or doing her any good, though it's been up for years. If you're like her, please let me know. I'd like to get a better idea of how many smart business owners are out there who are at a disadvantage by not knowing how to check their site's performance. I'd be happy to offer a free 15-minute phone tutorial to show them how. No obligation.