One in five of all married couples spy on each other's emails and text messages to ensure they are not cheating, say Oxford University researchers.

And 13 percent of those surveyed have confessed to checking up on the browser's history to find out what their partner had been surfing.

While many couples said the internet was useful for maintaining a relationship, they also admitted it could be a threat by opening up the opportunity for "online infidelity".

Unsurprisingly, 97 percent of respondents would be unhappy if their partner fell in love with someone else via the internet and 92 percent would not be pleased if their other half disclosed intimate details of their relationship to others.

When it comes to visiting adult sites, however, men and women have slightly different views on the matter, with men more likely to accept such behavior in their partner than women.

With more and more people finding love online, this factoid can prove useful: Namely, your date's profile on online networking sites (such as Facebook) can reveal whether he's actually a narcissist.

Researchers from the University of Georgia gave personality questionnaires to nearly 130 Facebook users and analyzed the content of their online profiles.

What they found is that the number of Facebook friends and wall posts (messages left by the owner of the profile or friends) that a person has correlates with narcissism. Laura Buffardi, a doctoral student in psychology, said this is consistent with how narcissists behave in the real world, with numerous yet shallow relationships.

A self-obsessed Facebook user will boast thousands of friends and update their "status" non-stop. "Sometimes they'll have a famous (Ralph Waldo) Emerson quote, but they'll include quotes from themselves or something flattering someone else said about them," Buffardi said.

And guess what, narcissists are also more likely to choose glamorous, self-promoting pictures for their main profile photos, while others are more likely to use snapshots. So if you see him posting photoshopped, look-at-me pics of himself, he probably has a narcissistic streak.