Would you be referring to the false doctrine of "sola scriptura" which is found nowhere in the Bible because it wasn't invented until the sixteenth century?
Just referring to any belief that doesn't have some type of biblical foundation whatsoever (particularly any foundation in what Jesus Christ or his Disciples said). There are plenty of these types of beliefs in every church, and they may or may not conflict with actual Scripture. Obviously, those that conflict are just flat out wrong. Those that don't conflict may be fine and dandy for making someone feel good, feel closer to God, feel closer to other Christians, etc., but they just aren't scriptural (meaning they are not "wrong" from a Christian perspective, but they are not "right", either).
If Christ didn't say something is necessary for my salvation and a church (because of its traditions or whatever reason) says it is necessary, care to guess which side I'm coming down on?
As a Protestant (and I would like to think if I were Catholic), whether Mary stayed a virgin after Jesus' birth is irrelevant. It has nothing to do with Jesus' life, death, and resurrection, nor my personal acceptance of Him as my Lord and Savior. I never really understood the whole point of arguing/spending time defending a belief that (from what I've read) is not based on Scripture and doesn't matter to my salvation.