It's Mouse Rage Syndrome, and it infects all Internet users sooner or later, according to a study of 2,500 Web users that was released Tuesday. Conducted by the Social Issues Research Centre in the United Kingdom, the study identified key factors that can negatively affect cardio functions, as well as the immune and nervous systems.

What's the root cause of Mouse Rage Syndrome? It's primarily caused by badly designed and hosted Web sites, according to the research center.

All Web surfers are familiar with the causes: slow-loading pages, layouts that are difficult to navigate, pesky pop-ups, and unnecessary ads, including banners. And, of course, the killer cause: site unavailability.

"The test results indicate that users want Google-style speed, function, and accuracy from all of the Web sites they visit, and they want it now," according to the SIRC report. "Unfortunately, many Web sites and their servers cannot deliver this."

In a test, the SIRC used as a control what it called "the Perfect Web site," one that functioned well. Study respondents were then presented with a stream of "crazy graphics and slow-loading pages." While a small sampling remained calm, others "showed very distinct signs of stress and anxiety," according to the study.

The report stated, "Some changes in muscle tension were quite dramatic While this was happening, the participants faces also tensed visibly, with the teeth clenched together and the muscles around the mouth becoming taught. These are physically uncomfortable situations that reduce concentration and increase feelings of anger."

Rackspace Managed Hosting commissioned the study. The U.K. firm's managing director, Jacques Greyling, said the study shows that businesses selling online have a duty to provide an Internet experience "as stress-free as possible." He added, "The message is clear: Businesses need to provide simple and easy-to-navigate layouts, whilst focusing on speed and uptime."