"Ohnosecond" is a technological word. It is that little period of time when someone realises they've made a mistake or something's gone wrong.
As you can imagine, ohnoseconds are quite short.
Imagine this, if you will: You're writing something for some website that you're a member of. It's a long document. You're new to the site and you don't quite know yet that if you are inactive for a certain period of time, you get automatically logged out. You are writing and researching like mad, but it still takes over half an hour.
And you carry on, completely oblivious to time passing.
You get to the end. You hit the "submit" button. Then, when the page is loaded, you decide to see who you can chat to, or maybe you just want to browse around the site.
Then you notice that your login name isn't there anymore. You've been logged out. and you haven't even realised it.
Enter the ohnosecond.
You think to yourself, AAAAHHHHHH! That's a whole half hour's work WASTED!!!
You sit back in despair, and then you think about the term "ohnosecond" and begin to see the funny side of it. You laugh out loud. You've gone from a gibbering, mad workaholic to someone at a stand-up comedy show.
Well, it could happen. And so could this:
You are just getting used to Mozilla Firefox after so many months with Internet Explorer. You have heard from a friend who has Firefox that you can open up several web pages with one program window, and that it's called 'tab browsing'. You explore for a bit and you eventually find the keyboard shortcut for opening up tabs: CTRL+T. Excited, you try opening up several tabs. They all work nicely.
So there you are, happily opening up tabs like a four-year-old, and you decide to write something else up for the same website you were writing to before. You open up yet another tab, and for once you type in the URL. You locate the site, and you start writing.
It's another long document. You are nearly at the end of another half-hour writing marathon, when you make a mistake. You decide to rectify it by pressing CTRL+W.
And then that tab closes.
And you have found, by accident, the keyboard shortcut for closing tabs on Firefox.
One ohnosecond later, you're in a foetal position and you're whimpering like a dog on a honeymoon. You've lost yet another half hour's work and you can't get it back.
Don't say I didn't warn you. They can, and do, happen.