The problem is that when you view the page in your browser, your browser
executes some javascript code that sets the value of the counter <div>.
However, when you use mechanize to access the page, mechanize retrieves
a text file containing the lines of javascript code as well as the
html--but mechanize is not a browser, so it cannot execute the
javascript code (nor does mechanize display the colors specified by the
html). All mechanize does is examine the text file for information.
Luckily for you, there are now advanced programs that can retrieve the
text file containing the javascript and html, load the file into a
browser(which executes the javascript), then the program can examine
what is actually displayed in the browser: