Depends on the university how well they track things. My university will track every lecture attended, and they put it on your results slip, and have words if it's an issue. If you're not missing other lectures though, the odd one here and there won't be an issue. I missed odd ones out of laziness, or for interviews, and i'm fine!
Whether the notes are online depends entirely on the lecturer usually. I had some that put everything online all at once, some that did it lecture by lecture, some that just missed some gaps out, and some that never ever even went near the blackboard tool.
You won't have a clear answer until timetables are released though. I had labs 1.30 pm - 5 pm on a Friday in my second year (chem). They're not completely adverse to scheduling things on Fridays :P it'll most likely be fine though, just wait and see.