Using Google Analytics to visualise the flow of visitors through a web site, is vital to understanding the marketing process and making sales.
The marketing funnel explains the sales process from first contact, through to conversion to sales, as a kind of funnel; wide at one end and thin at the other. The wide end represents the entire market, and the thin end represents the limited number of prospects who eventually make a purchase.
This analogy can be applied to any and all marketing processes, the purpose of which is to chivvy leads along from the opening exchange of information to the sale, through a number of interactions.
Web marketing is just one of the more recent incarnations of the marketing funnel, and various tools can be deployed to track the progress of leads through the funnel and seeing where they drop off the radar.

It stands to reason that increasing sales and customer value can be achieved by:
* Getting more leads in, by keyword research, social marketing, etc.
* Reducing lead drop-off; unwanted click-outs, loss of attention, etc.
* Increasing conversions; on-page marketing, sales letters, etc.

Google Analytics is a tool that can be used to track all three aspects, and it comes with a few new terms to become familiar with:
* Entry Pages; those pages that the leads see first
* Exit Pages; those pages that the leads see last
* Visitor Flow; the path of a visitor through the site.
For sites that are constructed with the marketing funnel in mind; to capture, inform, persuade, and convert leads to sales; the Visitor Flow function is extremely useful.

Using Visitor Flow to Map the Marketing Tunnel
The Visitor Flow shows the movement of traffic from one page to another. The traffic can be grouped by a number of factors, of which the default is geographical. The initial view shows (for the date range specified) the number of visitors per region, and the first pages that they visit.
These pages are the landing, or entry, pages, and each will have a little red stripe on the right hand side.
The visual importance of the red stripe is that it denotes drop-off: The thicker the line, the higher the drop-off rate. The first thing to note then, is that those pages with the largest red stripes are where marketers need to concentrate their efforts; it shows visitors leaving the site.
From these first pages, it is possible to follow the flow of traffic through the site, and usually two things will become apparent:
* At each step, there are less pages accessed
* For each page, there is less and less drop-off
At the far right; the diagram can be scrolled by dragging it with the mouse, is the ‘thin’ end of the funnel. It is here that the Call To Action page should be located, the place where the visitor; who has become a lead; is converted into a customer.
If the drop-off here is high, it is either because the visitor is leaving to go elsewhere, or because they have effected a purchase through the third party order and payment processor; ClickBank, for example.
It should be a simple matter to track this by comparing the number of sales of the product in question against the drop-off, which ought to give a good idea of the conversion rate.

There are a few points to note:
Firstly, if multiple revenue channels are tracked under the same Analytics project ID, then it is possible to pick up one thread by selecting the appropriate sales page, clicking on it, and choosing to view only that path through the site.
Secondly, drop-off can occur in either direction: visitors may click back at any point, and depending on the browser settings, that may or may not trigger the Analytics system. These visitors may get lost in the statistics, and so tracking them may require a different approach.
That approach may simply be to force a refresh and look for circular traffic patterns in the Visitor Flow, or detect the action and suggest an alternative (tracked) action to the visitor.
This last approach should also increase conversions, or at least provide a useful way to build a list of possible future customers.