The most accurate way to measure the success of your website is look at your website's statistics and study of the behaviour of website visitors. This is a really helpful way of working out what you are already doing right, and what you could do better. The tools you use to do this are called web analytic tools. There are various free tools available for doing this including Google Analytics.
The most important information to examine is the number of visitors or unique visitors since this figure gives the most accurate impression of a site's audience.
The site analytics will also show you Hits, however this number is misleading since it can overestimate the popularity of a site, because it counts the loading of every item on a page not the viewing of a page overall.
Other information which your website statistics will offer are as follows
Referring search engines
Details on which search engines delivered traffic to the website.
Referring keywords
Details on keyword phrases that were used to find your site. If people are using keywords to search for your site that you aren't using in your site content or metadata (the keywords you use to describe your webpage), then you could use this information to identify new keywords to include in your site in the future.
Unique monthly visits
It is good practice to monitor this on a monthly basis and measure it against the number of search engine referrals, so you know if your traffic is coming from people who knew your site already or were looking for something on a search engine.
Site paths (entry and exists)
This shows how many users entered a site per page and how many left per page. This is useful to check the effectiveness of high-ranking web pages. For example if a particular page on your website, such as your homepage,is used 100 times as an entry page for your site and only 10 users clicked beyond that page, 90% of the possible visitors were lost.