Log file analysis vs. page tagging
We all know that we should use web analytics to analyze website visitor behavior and online marketing channel performance. However, what kind of web analytics should we use? Should I go for log file analysis or page tagging or a bit of both? First, let’s define what we mean by these terms.
Page tagging involves putting a piece of code, usually externalized JavaScript, on every page of your site and is sometimes called client-side data collection. Each time a visitor’s browser opens a tagged page, the script is processed and the visitor’s information is collected. Log file analysis refers to the data collected by your web server. What is the difference from a web analytics point of view?
The bad news is that both strategies have their advantages and disadvantages, so here goes.
Labeling Benefits Page
o Because the data is collected on the client side, this fixes any proxy and caching issues
o It will give you information about web design parameters such as browser versions, platform versions, screen resolution, connection speed, etc.
o Client-side event tracking, such as JavaScript and flash events
Disadvantage Tagging Page
o Firewalls can prevent or interfere with script processing
o Configure costs associated with the insertion of code.
o Code insertion can lead to errors
o Will not catch page errors like 404
o Because robots ignore scripts they cannot crawl search engine spiders
o Cannot directly crawl non-html pages
o Vendor specific
Advantages of log file analysis
o Historical data can be analyzed
o Little installation cost
o No firewall issues
o Easily track page errors
o Can track search engine spiders
or Independent Provider
o Can crawl non-html pages such as PDF files
Disadvantages of the log file
o Proxy/caching inaccuracies. If a page is cached, no logs are recorded on your web server
o Without web design parameters
o No event tracking
If you’re used to looking at web statistics using Web Trends, for example, you may notice significant differences in the number of visitors. By moving to log file analysis, the number of visitors can increase by 20-30%. If your site does not use persistent cookies, your web analytics program cannot identify unique visitors, therefore all visitors are grouped together as a total. Unique visitors typically account for 20-30% of total website visits, so this metric will be inflated by this amount. Sometimes you will see a dramatic reduction in site visits. This is usually because web analytics programs remove the load of graphics that other programs mistakenly count as visits.
Other differences in the number of visitors are generally due to how the programs define a visit. A visit duration of 30 minutes means that multiple visits from the same IP address within this time period will count as one visit. Change this parameter to 15 minutes and these visits could be counted multiple times and your total visits will increase. Finally, when a web browser loads a PDF file, it fetches different parts of the file at different times, and some programs may count this as multiple requests for the same file. A good web analysis program will collapse these multiple downloads into one.
It’s important to understand these differences and manage your peers’ expectations, as surprise drops in website metrics can sometimes lead to disenchantment with measuring website performance as a whole.
For more information on web analytics, please contact us at http://www.ju2.com and keep an eye on our blog at http://www.ju2analytics.com