...that these signify topics on which you have posted? Other topics will display with a file folder. At the bottom of each forum topic listing there is a legend with the various other symbols. You can not change these. They signify the status of the topic and are set by the system. The yellow one means that there are new posts since you last visited the thread and the grey one means there are no new posts since your last visit. The little guy (mini-you) can be handy if you are making a quick pass through the forum and just want to check in on topics you have posted on and there you go.