The case of Bank of Ireland chief executive Mr Michael Soden, who resigned last weekend after admitting to having used a work PC to view an improper website, highlights two points that are often poorly understood by those who use the internet. Karlin Lillington

The first is that looking at questionable sites while at work, using work-owned computer equipment, is for many companies a firing offence at worst, and seriously damaging to an individual's career and reputation at best.

The second is that, even if you try, it is extremely difficult to totally remove the digital traces of where you have been Web surfing, even for the professionals and the most adept computer hackers.

The moral of the story is don't be stupid and do things in work in an online virtual world that you wouldn't or shouldn't do in the concrete world - in this case, the digital equivalent perhaps of reading Playboy magazine then storing it in your desk.

Not that looking at an escort site for Las Vegas is a particularly shocking or, by Las Vegas standards, an unusual, offensive, or questionably legal thing to do.

Folks, please remember that Las Vegas proudly goes by the moniker Sin City - even local tourist sites use the term.

Gambling, strip clubs, nude reviews, topless shows in all the big hotels - this isn't exactly Disneyworld.

One major hotel/casino, The Palms, even offers "stripper poles" in some of its rooms, according to the Lasvegas.com website.

To give a little perspective, Lasvegas.com, a major city tourism website, lists this factoid in its "50 Ways to Love Las Vegas" feature story.

Some mainstream Las Vegas websites actually link to escort agencies because, don't forget, escort agencies are perfectly legal in Las Vegas.

They are even advertised on billboards all over the city.

Heck, prostitution, like gambling, is legal in the State of Nevada.

So Mr Soden was hardly delving into some hardcore underground porn site. So mainstream are Vegas escort services that he likely could have clicked over from many high-profile hotel websites.

To my mind - and yes, I am a liberal Californian who grew up in the 1960s, I'll confess that now - this is such a mild transgression that I'm surprised it was considered a resignable offence.

I am sure plenty of readers will squirm knowingly when I say I can guarantee right now that many if not most offices are chock full of employees - maybe you - that have looked at a lot worse online, on company time.

Nonetheless, most of us know when we are looking at a site that would not be considered appropriate while at work.

Would you keep it onscreen if your boss, a co-worker, or a child were looking over your shoulder?

Then it is probably the type of site whose viewing falls into the improper behaviour category of many company policies.

For some reason, as with so many other areas of online life, we are guilty of viewing our online lives and activities as more hidden and less accountable than our real-world lives.

This is particularly true of office environments.

People view sites and send questionable emails and picture or sound file attachments while at work when they would never arrive in and pass an armload of Hustler back issues to their cubicle neighbour.

Such casual indiscretions are a major headache for corporate legal teams because there is little clear-cut case law in the area of liability for offensive emails, attachments, Web viewing, or postings to chatrooms or bulletin boards made by employees on company time.

And few people do not violate company policies, even if only inadvertently, on what is allowable viewing during company time. Given the explicit material that now arrives regularly in company inboxes as spam - unsolicited commercial email - and given the kind of thing a well-intentioned friend might email for you to read at your desk, who can totally avoid having some offensive material on their PC?

The flip side of this situation is the case of those who look at such material knowingly on a work (or for that matter, home) computer, thinking it is a matter between them and their browser.

Wrong. You leave little trails on your computer everywhere as you move through websites, from URL information to cookies that enable a site to recognise you on your next visit. Even if you go in and empty the cache (the short-term storage area of your browser that remembers which pages you've visited), all the information is still there on the hard drive, and very easy to find by someone looking for such information.

Routine procedures, such as that which brought up the site on Mr Soden's computer, can reveal where you've been if you've made no attempt to expunge such information.

Even professional programs designed to delete incriminating information don't work thoroughly, according to computer forensic experts I've spoken to over the years.

About the only way to completely erase information on a hard drive is to destroy it. That's why the CIA puts its old hard drives through an industrial drill press to make them nothing more than scrap.

We all tend to think the internet is a place where we can travel incognito; where, as the famous New Yorker cartoon put it, "no one knows you're a dog".

That may be true. But it's pretty easy to know where that dog has been.