For the past several years, the US Patent Office has been encouraging practitioners to use its electronic file wrapper system. The system, known as PAIR, contains all sorts of information on pending and issued patents including: filing data, foreign priority, patent family data, and a full prosecution history.
Until this weekend PAIR operated through a static URL system. That meant that you could bookmark the PAIR page for your pending applications or e-mail the link to your clients, the inventors, or even potential licensees. I also used this feature to obtain information for my statistical studies and have written several bits of code to automatically download and preformat information regarding selected patents.
Now, without public notice or comment, the PTO has removed the static URL system and replaced it with a session-cookie based system that monitors a particular computer's activities and does not allow for bookmarking or other delayed or preformatted access.
Advice: What would really be useful would be to have a system that allows for automatic updates of PAIR data, such as an RSS feed. Unfortunately, the PTO has taken a technological step backward.