If you've looked into your website statistics using a tool like Google Analytics, you've almost certainly come across the words 'Bounce Rate'. What does bounce rate mean?
Google Analytics is a way in which to measure the stats for your site, enabling you to see which pages are working well and which ones aren't. Your traffic sources, the keywords people are using to find you and a lot of other useful information can be found here.
Bounce Rate Explained
According to Google Analytics, the bounce rate is simply the percentage of single-page visits to your site - where the visitor arrived at your site, looked at the information on the page they landed on and then left without going onto any more pages. It doesn't have to do with the time they spend on the site. The visit can last a second or 10 minutes, but if they only visit one page before leaving the site, it's considered a 'bounce'.
It doesn't always mean that the visitor left because of the content on your site. It may be that they stayed on that page to read the entire page, post or article, got the information they were looking for, and then left.
Generally speaking, it is belived that the higher the rate, the worse the site is performing. However, that isn't necessarily true. Certainly, if 95% of people arriving at your site leave straight away, then you need to look at both the way you're driving traffic to your site (building the visitor's expectation) and also at the landing pages they reach when they arrive.
If you look in Google Analytics, under Traffic Sources > All Traffic Sources on the left sidebar, you'll see that all the sources have their own bounce rate. The site bounce rate is the average of all these sources. By looking at this broken down version (under 'All Traffic Sources') you can see the places that you're getting traffic from where the visitors are staying and exploring the site, as well as those sources where they're leaving immediately.
If you have a higher rate (above 70%) - this may be a reflection of other factors - not just the suitability of your site to your visitors.