To read the newest messages since you were on the forum you must be logged in and have Cookies enabled on your browser and they must not be deleted from the last time you were online - some browsers are set to delete cookies upon exit.
If cookies are enabled, to view the newest topics since your last visit, just click Active Topics
in the upper-right of the screen.
Once at that screen, there will be a couple of options. You can view topics from your last visit or the last two hours, day, week, month, etc. Also, you can reload the page at intervals of one minute, five minutes, and more. This way, if you keep the screen open during the day you will be able to see the newest topics and responses as they are posted.