In marketing, a conversion occurs when a prospective customer takes the marketer's intended action. If the prospect has visited a marketer's web site, the conversion action might be making an online purchase, or submitting a form to request additional information. The conversion rate is the percentage of visitors who take the conversion action.

Win-loss analytics involves identifying and analyzing the reasons why a visitor to a website was or wasn't persuaded to engage in a desired action (conversion).

This information allows web teams to improve the website's navigation and content, identify individuals that are more likely to convert, to improve marketing efforts

Web analytics is the measurement, collection, analysis and reporting of internet data for purposes of understanding and optimizing web site usage.

There are two categories of web analytics; off-site and on-site web analytics.

Off-site web analytics refers to web measurement and analysis irrespective of whether you own or maintain a website. It includes the measurement of a website's potential audience (opportunity), share of voice (visibility), and buzz (comments) that is happening on the Internet as a whole.

On-site web analytics measure a visitor's journey once on your website. This includes its drivers and conversions; for example, which landing pages encourage people to make a purchase. On-site web analytics measures the performance of your website in a commercial context. This data is typically compared against key performance indicators for performance, and used to improve a web site or marketing campaign's audience response.

Historically, web analytics has referred to on-site visitor measurement. However in recent years this has blurred, mainly because vendors are producing tools that span both categories.

The remainder of this article concerns on-site web analytics.

Many different vendors provide on-site web analytics software and services. There are two main technological approaches to collecting the data. The first method, logfile analysis, reads the logfiles in which the web server records all its transactions. The second method, page tagging, uses JavaScript on each page to notify a third-party server when a page is rendered by a web browser. Both collect data that can be processed to produce web traffic reports.

In addition other data sources may also be added to augment the data. For example; e-mail response rates, direct mail campaign data, sales and lead information, user performance data such as click heat mapping, or other custom metrics as needed.

Google Analytics (abbreviated GA) is a free service offered by Google that generates detailed statistics about the visitors to a website. Its main highlight is that the product is aimed at marketers as opposed to webmasters and technologists from which the industry of web analytics originally grew.

GA can track visitors from all referrers, including search engines, display advertising, pay-per-click networks, email marketing and digital collateral such as links within PDF documents.

Integrated with AdWords, users can review online campaigns by tracking landing page quality and conversions (goals). Goals might include sales, lead generation, viewing a specific page, or downloading a particular file. These can also be monetized. By using GA, marketers can determine which ads are performing, and which are not, providing the information to optimize or cull campaigns.

GA's approach is to show high level dashboard-type data for the casual user, and more in-depth data further into the report set. Through the use of GA analysis, poor performing pages can be identified using techniques such as funnel visualization, where visitors came from (referrers), how long they stayed and their geographical position. It also provides more advanced features, including custom visitor segmentation.

Users can officially add up to 50 site profiles. Each profile generally corresponds to one website. It is limited to sites which have a traffic of less than 5 million pageviews per month, unless the site is linked to an Adwords campaign.

There are no globally agreed definitions within web analytics as the industry bodies have been trying to agree definitions that are useful and definitive for some time. The main bodies who have had input in this area have been Jicwebs(Industry Committee for Web Standards)/ABCe (Auditing Bureau of Circulations electronic, UK and Europe), The WAA (Web Analytics Association, US) and to a lesser extent the IAB (Interactive Advertising Bureau). This does not prevent the following list from being a useful guide, suffering only slightly from ambiguity. Both the WAA and the ABCe provide more definitive lists for those who are declaring their statistics using the metrics defined by either.

Hit (internet) - A request for a file from the web server. Available only in log analysis. The number of hits received by a website is frequently cited to assert its popularity, but this number is extremely misleading and dramatically over-estimates popularity. A single web-page typically consists of multiple (often dozens) of discrete files, each of which is counted as a hit as the page is downloaded, so the number of hits is really an arbitrary number more reflective of the complexity of individual pages on the website than the website's actual popularity. The total number of visitors or page views provides a more realistic and accurate assessment of popularity.

Page view - A request for a file whose type is defined as a page in log analysis. An occurrence of the script being run in page tagging. In log analysis, a single page view may generate multiple hits as all the resources required to view the page (images, .js and .css files) are also requested from the web server.

Visit / Session - A series of requests from the same uniquely identified client with a set timeout, often 30 minutes. A visit is expected to contain multiple page views.

First Visit / First Session - A visit from a visitor who has not made any previous visits.

Visitor / Unique Visitor / Unique User - The uniquely identified client generating requests on the web server (log analysis) or viewing pages (page tagging) within a defined time period (i.e. day, week or month). A Unique Visitor counts once within the timescale. A visitor can make multiple visits. Identification is made to the visitor's computer, not the person, usually via cookie and/or IP+User Agent. Thus the same person visiting from two different computers will count as two Unique Visitors.

Repeat Visitor - A visitor that has made at least one previous visit. The period between the last and current visit is called visitor recency and is measured in days.

New Visitor - A visitor that has not made any previous visits. This definition creates a certain amount of confusion (see common confusions below), and is sometimes substituted with analysis of first visits.

Impression - An impression is each time an advertisement loads on a user's screen. Anytime you see a banner, that is an impression.

Singletons - The number of visits where only a single page is viewed. While not a useful metric in and of itself the number of singletons is indicative of various forms of Click fraud as well as being used to calculate bounce rate and in some cases to identify automatons bots).

Bounce Rate - The percentage of visits where the visitor enters and exits at the same page without visiting any other pages on the site in between.
% Exit - The percentage of users who exit from a page.

Visibility time - The time a single page (or a blog, Ad Banner...) is viewed.

Session Duration - Average amount of time that visitors spend on the site each time they visit. This
metric can be complicated by the fact that analytics programs can not measure the length of the final page view.

Page View Duration - Average amount of time that visitors spend on each page of the site. As with Session Duration, this metric is complicated by the fact that analytics programs can not measure the length of the final page view.

Page Depth / Page Views per Session - Page Depth is the average number of page views a visitor consumes before ending their session. It is calculated by dividing total number of page views by total number of sessions and is also called Page Views per Session or PV/Session.

Frequency / Session per Unique - Frequency measures how often visitors come to a website. It is calculated by dividing the total number of sessions (or visits) by the total number of unique visitors. Sometimes it is used to measure the loyalty of your audience.