I don't know if it's common to refer to multi-tier architecture layers by their numbers. I mean something like: "Argh, the date is presented in a reverse format, it must be a layer-one bug", or "The layer two seems to be really inefficient". Well, I know many people who uses that jargon.
If you are among them, please make me a favor: don't use numbers to identify software components or layers. Not when talking to me at least.
- You don't really save much saying "layer one" instead of "presentation layer", "layer two" instead of "application layer" and so on.
- I don't know how many tiers or layers you are supposed to have, so I'm unable to make sense of any number greater than one.
- I'm stupid, so I always forgot if the first layer is the user interface or the more basic layer which support everything else. So even "layer one" is meaningless for me.* I'm not impressed by the words "layer" or "tier". Not even if they are followed by a number.