Some sites, like Discovery’s Planet Green, have already been playing around with the new OPA ads, but if you haven’t seen them yet, you can do it with a little bit of imagination. Think of a traditional Web ad as the equivalent of a yard sign. The new ones are billboards.

Like your descriptions more literal? Here’s the technical description of the new formats. By way of comparison, the column of text you’re reading now is 350 pixels wide.

The Fixed Panel: 336 wide x 700 tall, remains constant as the user scrolls to the top and bottom of the page.
The XXL Box: 468 wide x 648 tall, opens for seven seconds to 936 wide x 648 tall with 1/24x frequency.
The Pushdown: 970 wide x 418 tall, opens to display the advertisement and then after seven seconds, rolls up to 970 wide x 66 tall, with 1/24x frequency.

And um, here’s what a really big ad might look like on your desktop (click to enlarge).

If you’re knee-deep in the online advertising business, you’ll be interested in why these ad formats are being pushed by the Online Publishers Association instead of the better-known Interactive Advertising Bureau. I have heard some baroque/petty descriptions of squabbling between the two groups, whose membership overlaps but isn’t identical. But maybe we’ll come back to that some other time.

For now, let’s see if these deliver as advertised–that is, whether they get marketers to spend more money on the Web, without just plowing the money into Google (GOOG).