A01 chaf6542 06 se fm indd

Sources  of   over‑  counting

Caching in user’s web browsers (when a user accesses a 

previously accessed file, it is loaded from the memory of 

the user’s computer on a  server-  based cache on their PC)

Frames (a user viewing a framed page with three frames 

will be recorded as three page impressions or page views)

Caching on proxy servers (proxy servers are used within 

organisations or ISPs to reduce Internet traffic by storing 

copies of frequently used pages)

Spiders and robots (traversing of a site by spiders from 

different search engines is recorded as page impressions. 

These spiders can be excluded, but this is  time-  consuming)

Firewalls (these do not usually exclude page impressions, 

but they usually assign a single IP address for the user of 

the page, rather than referring to an individual’s PC)

Executable files (these can also be recorded as hits or 

page impressions unless excluded)

Dynamically generated pages, generated ‘on- the-  fly’, are 

difficult to assess with  server-  based log files

Table 12.6

Inaccuracies  caused  by   server-  based   log-  file  analysis