Locate the copyright page (page ii, but it's not numbered: this is on the back of the title page which shows the book name in color and just across from the "Contents at a Glance" page)
On the middle of the page is a line of numbers looking like this:
03 02 01 00 7 6 5 4 3 2
The rightmost number on this line indicates the printing (the above example would be for the second printing).
Addendum to 3rd, 4th, and 5th Printings
Page 330, figure caption:
There are also problems with the spelling and accents for German and Spanish; the use of Simplified Chinese characters will cause difficulties for users in Hong Kong and Taiwan. This latter issue is particularly important: when we run usability studies that involve Chinese users, we always try to include both Simplified and Traditional regions (assuming a written interface; auditory interfaces obviously have to include Mandarin, Cantonese, etc.).
Errors in 2nd and 1st Printing (Fixed in 3rd Printing)
Page 34, figure caption: slope of recent transitions is 1% per week, not per year.
Pages 40-41: Figure captions are reversed. Page 40 shows Internet Explorer 3.01 and page 41 shows Netscape 4.01.
Page 209: Figure caption refers to a different example than the one used in the book. Correct caption: "In this example, I was interested in HTML tools for web design, and a click on that option would give me a list of the tools. But the display provides additional breadth by also showing me the other types of web design tools discussed on the site. Stepping up one level takes us further from the user's current interest, so less breadth is provided. The third column indicates that more information is available about other Internet-related issues, but these topics are not described in as much detail as the Web design tools. Going one step farther up, the second column lists other computer-oriented topics, but this level is described at a very coarse level of granularity."
Also, some smaller typos were found and corrected.
Errors in 1st Printing (Fixed in 2nd Printing)
Page 35: The word "gizmo" is missing from the second paragraph.
Page 395: The names of Louis Rosenfeld and Peter Morville are misspelled.
My apologies to Louis and Peter!
This is twice as embarrassing because these guys are my good friends.
Also, many smaller typos were found and corrected.