If you use other web analytics tools on your website, in some rare cases you may find that Piwik tracks a lot less visits than other tools.
While there are explanations for small differences, sometimes Piwik will track a lot less visits but about the same number of pageviews (actions). When this happens, it shows that the algorithm attributing Visits to particular pageviews is not working as expected.
If your website visitors are visiting from one IP address (eg. they connect from the same offices), then Piwik may mistakenly believe all actions by this IP address are the same. In this case you can set a setting in the config file, make a change to your config file as explained in this FAQ.