One of the most useful and important tips I ever heard about running a marketing campaign is "inspect what you expect."

In other words...don't assume the printer, the web designer, the merchant account service or any other aspect of your Internet marketing campaign will just automatically do as they are supposed to. Don't think someone won't drop the ball or have a brain fart at the absolute worst time.

Inspect your Internet marketing system -- every detail of it -- before and during the launch.

Good advice isn't it?

You're dang right it is.

In fact, it's so important...and so ultra critical...I completely ignored it recently and lost a bundle of money as a result.

Let me explain what I mean.

You see, so far just about all the ads I've written have paid out and are winners. There have been a few flops here and there where I tried selling to a market I didn't really understand. But the majority have pulled and pulled well.

Except for this one ad my client and I had up for about three months.

Even though it was for a very rabid market that loves to buy...and even though I'm very familiar with that market...the ad didn't pull even one single order in the three months it was up. And I mean nothing. Nada. Zippo.

Of course, it could be I simply penned a crappy ad.

But even that didn't explain zero sales. Especially in this particular market, where even a crappy ad pulls at least some response.

But for some mysterious reason...no matter how much I tweaked the copy, no matter how low we cut the price...we couldn't produce a single sale.

And this drove me absolutely crazy.

I became obsessed with making it work. I revised it dozens of times. Played around with it. Let other copywriters and Internet marketing friends of mine read it and then revised it again. And still no sales.

I was almost ready to write the entire thing off as a dud.

And then it happened.

A few weeks ago my client got an email from someone who wanted to buy the product.

He was a customer who kept trying to order...but said the order form wasn't working. It wasn't taking his credit card numbers. And the only price that appeared was the cost of shipping.

Doh!

Turns out there was a small glitch with the shopping cart software my client uses. And it wasn't working properly.

Now, we'll never know exactly how many sales that stupid little mistake cost us. But judging from the response we're getting now -- about 3% -- I'm guessing we flushed at least $10,000 in sales down the toilet.

Obviously, if we'd simply followed the "inspect what you expect" mantra -- this never would have happened. We would have noticed the software glitch and nipped it in the bud.

But you know what the real irony is?

Other than the fact nobody phoned their order in (which is another topic for another time)...this is actually a classic Internet marketing blunder routinely committed by seasoned gurus and amateurs alike all the time.

I'd heard about this sort of thing happening hundreds of times. It's in almost every good marketing and copywriting book I've ever read. It's happened to just about every serious marketer I've ever met.

In fact, our situation is a joke compared to the hair-raising screw ups involving multi-millions of dollars being flushed down the toilet because the marketer's secretary gave the ad rep the wrong 800 number or something to that effect.

Now, you may be tempted to think, "no way will I ever make such a stupid mistake."

And I hope you're right.

But it's a lot like not regularly backing up your computer's hard drive.

If you get lazy and refuse to sweat the details (as I did in this case) you'll eventually get nailed.

Anyway, the moral of the story is make sure you inspect what you expect every time.

It only takes a few minutes to check your order form, see what your ad looks like on multiple browsers, verify your third party merchant account service (if you use one) is standing by and not performing "routine maintenance", and all the other boring, mundane things we love to let other people handle.

And yet...those few minutes can make all the difference at the end of the day.