Up until now, you had to manually type in your username and password for the first message posted during any browser session. This problem is fixed for new members who join after November 23rd.
Current members will have to go to the Preferences page (a link to this page also appears on the top right of the Forums Summary page) and select yes on the line where it says, "Store Username and Password in browser memory for 1 year," then click on Submit Preferences. The next time you post a message should be the last time you have to type your username and password. For a year, at least.
Technical information follows for those interested.
The Date.getYear() call is now deprecated for the more consistent Date.getFullYear(), which returns 4 digit years for all browsers. I've changed the code to use Date.getFullYear() everywhere.