The traffic could be generated by a script or program.

The traffic could be coming from an auto-surf exchange.

The traffic could be generated by spyware/adware programs.

The traffic could be auto-refreshed to rotate campaigns.

Generally you can tell if traffic is real or not by trace routing the IP addresses of the visitors. Fake traffic tends to have very high percentages of anonymous proxy addresses or dead-end/not-in-use IP addresses. If the traffic is being generated through an auto-surf exchange or if the traffic is being auto-refreshed, you will be able to tell by the length of the visits. If you see that the majority of the visitors are all staying for exactly the same duration of time, then odds are is that auto-surfing or auto-refreshing is to blame.

Something else to be weary about is low cost expired domain traffic. In this day and age, it is a very difficult task to get your hands on a domain that still receives a ton of traffic. This is due to the fact that major search engines, such as Google, pick these expired domains out of their search results as soon as they can. Why ? Because expired domains hurt the quality of their search results. However, it is possible to find expired domains that still get traffic from means other than search engines, but this breaks down to a pretty hefty CPM (cost per thousand) price.

For example, let say that you manage to find 10,000 expired domains that each still get 100 visitors a month.

10,000 * 100 = 1,000,000 a month.

1,000,000 * 12 months = 12,000,000 a year (12,000 CPMs).

Assuming that you're paying a rate of $7 per domain for yearly registration, you're spending:

$7 * 10,000 = $70,000 per year

That works out to:

$70,000 / 12,000 CPMs = $5.83 per CPM

That's right, in our example the base CPM price figures out to $5.83! And that's before any mark-up is added.

So if a web traffic supplier sells traffic hits at a rate of $3/CPM and tell you they are redirect traffic or expired domain traffic, you now know that they are not real expired domain hits.

Popunder web traffic advertising is now mostly use by genuine web traffic providers.

A pop-under is like a pop-up except that it loads underneath the current web page rather than over it.

This form of advertising is much more superior because it is less intrusive. Unlike pop-up windows that load over your web page, pop-under windows quietly load under your web page. Your visitors probably won't even see the pop-under window until they're finished at your site and close the window.

The effectiveness of pop-under windows most likely stems from the timing. When your visitor first enters your site, their mind is on what lead them to your site to begin with. Pop-up windows will most likely cause a higher percentage of your visitors to instantly close your window before viewing its content. That's what makes pop-under windows more effective -- your visitor is through visiting your site and their mind is clearer. They will be much more likely to take the time to look at your offer when they don't have another objective on their mind.

Generating web traffic from popunder advertising is also very much cheaper then generating traffic from expired domain traffic and is the number one choice of most web traffic providers.