A paper published in ACM Transactions on the web in February 2008 takes a detailed, and scientific look, at peoples behaviour on websites.
Backtracking through a site is no longer so popular, back button usage has been replaced by multiple tabs. Scanning text, rather than reading it, remains the norm. These are the results of work published by researchers who examined peoples behavior in a long term study and compared it with similar studies from the mid ‘90s.
Here’s the reference:
Weinreich, H., Obendorf, H., Mayer, M. (2008). Not Quite the Average: An Empirical Study of Web Use. ACM Transactions on the Web. Vol.2. No. 1.
Their results can be divided into:
The new character of web navigation:
The most significant change is the increased number of pages opened in new windows (reflecting the introduction of this feature in modern browsers), the raised importance of form submissions and a decrease in back button usage. The back button is functioning more as an ‘undo’ tool.
The speed of web navigation:
Only 10% of all visits were longer than two minutes. 75% of all pages were viewed for less than 10 seconds. 25% of all pages were viewed for less than 4 seconds. Pages visited for less than 4 seconds had an average number of 430 words – far more than can be read in that time.
Jakob Nielsen takes a more detailed look at this – How little do users read?