I've already mentioned testing the user experience before launching a campaign to make sure the experience is consistent with the expectations of the advertiser. Another user experience sanity check that needs to be conducted before launching an online campaign is the mindset check.
A client of ours once tried to run an ad that took nearly 30 seconds to run through its animation sequence on a site where the typical user was in and out in half that time. Obviously, folks didn't stick around long enough to see that ad play out. But that's just one symptom of an overarching disease.
The sanity check has to do with the mindset your prospects will tend to be in when they encounter your ad. Are they browsing? Are they "mission critical?"-- that is, are they preoccupied with hurriedly completing a specific task? Are they on a page that typically serves as a quick gateway to another?
Ignore mindset at your peril. Many advertisers filter inventory from their buys based on mindset. They might not buy ads on Instant Messenger applications, knowing that people are less likely to respond if they're actively engaged in a chat with a buddy. They also might ignore proposals to buy ads on stock quote pages, knowing that even the desirable individual investor target can be less attentive if they're quickly typing in one stock quote after another as they check on prospective investments.
Creative can be optimized according to mindset. One might use a short-form animated banner on a gateway page and a longer form creative on a page where people are likely to spend more time. But mindset shouldn't be ignored. Doing so can reduce the effectiveness of your campaigns and cause perfectly good inventory to fail to produce brand impact and increased response.