venial sin

Apparently, I didn't learn from my RCIA disaster, because last night, I acted cowardly again! I was helping out someone on her blog, when this modernist made this very erroneous and damaging comment, I considered saying something, but decided to ignore it. It was not until late that it sunk in...

Can someone please provide a list of methods, by which, venial sins are removed? Also I'm confused about certain practices in the mass, I've heard some people say things like, the penitential rite removes venial sins, while others say they don't. Can someone please sort all this out?