NONE: Re: ONLINE-ADS>> Caching, IE and Guaranteed Impressions

Re: ONLINE-ADS>> Caching, IE and Guaranteed Impressions

Cliff Kurtzman (
Fri, 4 Apr 1997 11:48:27 -0600

Andy Bourland <> wrote:

>The bottom line effect of all this is that if there is a good number of
>IE users cruising your site, a significant percent of your ad banner
>impressions are going unrecorded.
>We came up with a fix for this, but first I want to check and see if
>there are others who may have encountered this. Is this consistent with
>what you found? How did you work around it so that all ad impressions
>are counted?


We report page impressions rather than graphic loads. MSIE is not the only
browser that caches. And many systems, like AOL, Compuserve, and WebTV
cache as well. We have found that the number of people that have graphics
off or do not fully load the page is not very significant -- and even if
they have graphics off, they will still see both the ALT tag and the ad
line of text we always let our advertisers include with their banner. We
have found on some of our pages that simply counting graphic hits under
reports true activity by as much as 50%.

One implication of this is that if someone or some ad network wants to
serve up their banner on your page but off of their own server, or to put
an invisible graphic on your page that runs off their server for the
purpose of activity verification, they may undercount activity by a
significant percentage. WebConnect/WorldData does this with the banners
they place on sites, which unfortunately could cause their clients to
believe the exposure a site delivers is far less than is actually promised
and delivered.

Some things you can try are:

1) Put a ? followed by some random text after the name of the graphic in
your IMG tag. The browser will still load the graphic just fine but may
think it is a cgi so it will retrieve the file from the server.

2) As Ken Jenks <> wrote to this list back in October,
you can apply the Pragma: nocache directive in a couple of ways, including
for individual images (like banner ads). This means that most of your page
will be cached, but your banner ad won't, so you can re-load a different ad
every time.

One other problem you may have noticed is that your banner counts and
especially your click-through counts are becomming highly over-inflated due
to activity of robots and offline downloaders. One way we have found to
mitigate this problem is to place ad graphics and ad redirects on a
different virtual host from the host on which the ad is being served. The
offine downloader may be configured to only load files from your host, so
it won't create a false click-through on a redirect that appears to be on
another host. This is not necessarily 100% effective, but it has seemed to
help a great deal.


Cliff Kurtzman
The Tenagra Corporation


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