You're right, this is a pretty darn big issue, but it turns out that there is one key to a really successful advertising campaign online, one key idea that a surprising number of companies fail to do.

The key? Create a custom landing page for each of your creatives

Whether it's a text-only pay-per-click AdWords advertisement or a expensive Flash-based graphical advertising campaign, your ad promises the viewer something, be it a product, service, discount, or even just more information. The landing page then has to deliver on that promise.

Let's look at an example I just noticed today on the New York Times web site, an expensive campaign from Hewlett-Packard, a company that should definitely know better. On the NYT home page, there's the following attractive ad:

I admit it, I was hooked and quite curious about the gadget shown. So I clicked on the ad, and was taken to the generic HP Shopping site, with no clue about the product that had caught my attention:

That lack of a custom landing page, that lack of follow-through, really cripples this campaign and while I might even have considered purchasing the gadget - whatever it is - I'm sure as heck not going to dig through the entire product catalog to find the device they paid so much money to advertise on the NY Times.

Can you see the disconnect here and why HP lost a potential sale, even having produced some interesting creative and positioned it on the New York Times home page? If the landing page would have been more information about the product, and even perhaps a special discount offer for Times readers, they might have closed the sale. As it is, however, they just left me shaking my head, wondering why they hadn't done better.

So that's my #1 suggestion to you for online advertising. Hope it's helpful!