A supposed horror is being late for an interview.  I got my highest paid and best job as a young whipper snapper from an interview where I showed up two hours after the time I should have done. 
And I just did an interview where the person was late - got lost, traffic, dog eat my car etc. - but nobody was that bothered and were more interested in asking questions

I don't recommend going to interviews late but if you do then don't let it throw you.  If you do a good job of answering questions, impress them with your skills and have a half-decent excuse you might do just fine.