the white background should just be part of the flashing for a Hot Topic. My guess is that gif was not made as a transparent one is why you see the white background. That would be a screw up on the image creator imo.
Ones with the two squares on top of each other are a sticky. You can right click on an icon and look at the properties and it will tell you the icon name and it should explain what it is. Its pretty self explanitory
This link shows the stock icons and their functions http://www.phpbb.com/community/viewtopi ... 5#p6348265
Since this site is running a modified theme. You would have to download that theme to extract the icons and their names to get a complete list like the link above.
Edit ok here is what I could grab easily off this site.
Forum with subforums Read
Topic Locked Read
Sticky Read That you have posted in
Topic Read you have not posted in
Topic Read you have posted in
Hot Topic Read you have posted in
Topic Unread you have posted in
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