Catfish style interruptor ad - does Google penalize?

[DirigoDev]

We’re looking at doing a “catfish” style interruptor that comes up from the bottom of the browser to greet a first time visitor and deliver a welcome promo offer.

We’ve heard that Google doesn’t look favorably on them. Does anyone know anything about Google’s point of view on them or how severely we might be penalized?

The technique uses JavaScript and a negatively positioned image:

<div style="margin-bottom: 0pt; height: 138px; bottom: -40px;" id="catfish">

I know that Google does not like such techniques. What should we do?

[edited by: tedster at 7:26 pm (utc) on April 7, 2008]

[tedster]

I'm not sure where you might have heard this, but in my experience it's not true. There are all kinds of legitimate reasons to initially position a div off screen - or even have it begin with a display:none rule. As long as something can trigger the display for a visitor (in this case, no cookie is the trigger to move the positioning up, I assume), I've never heard of a problem with Google, not even for a human review.

[Bewenched]

I would just make sure that it never covers any adsense ads if you run them.