1x1 pixel gif is not always loading

Tracking experiment unsuccessful

[geekay]

As an experiment I put, on some of my pages, a 1x1 pixel gif (with a different file name for each page) that is to be automatically loaded each time the page is loaded. I thought this might give me some idea of how often a page is viewed exclusively through search engine caches. (As far as I know SE caches only hot-link to images.)

But it doesn't work. All the gif's are requested roughly one third LESS frequently than the corresponding pages.

I don't think one third of the viewers are browsing with images disabled. Neither do I believe that that many gif requests are returned with a 304, although pages may be altered, gif's not. The answer is probably quite simple. Would anybody care to tell me?

[neo_brown]

Not sure but...

If someone accesses your site and looks at the same page 3 times, perhaps your logs will reflect the page being called but the image itself may well be cached in the clints browser.
Like I said Im definatly not sure on this one, just a possibility.

**Additionally, this is the method many large commercial email companies use to moniter their impressions.

[larryn]

gee,

Did you disable caching for that 1x1 pixel gif? If not, then if the image is already cached by the local browser, the browser might decide to us that local copy instead.