Icon question

I have a random question. I was looking at the various threads being posted and I noticed some have a red envelope beside them and some have a yellowish/whitish envelope.

I know it's not due to whether or not I have opened the thread, since there are threads I've read and or responded to in both colors. I know its not whether or not there are new posts or if I'm subscribed.

I know it is completely not important, but now its bugging me that I can't figure this out. I skimmed through the FAQ but did not see any answers (no, I did not read it in depth). I even searched old threads, but apparently no one has ever mentioned it before.

Anyone know what I'm talking about?

no i do not pay attention but im curious

Red means it has lots of views or posts.
White means it does not.

If you scroll to the bottom of the page with the threads listed, you will see a guide.

saywhatkid said:

If you scroll to the bottom of the page with the threads listed, you will see a guide.

Click to expand...

See? I knew the answer had to be posted somewhere and I just couldn't find it.

Thanks! :P