They seem to be allowed as I can see both my insert triggers listed under the table with different names. Is it common or a bad practice? I am using SQL Server 2005
Yes, you can definitely have more than one trigger for each operation, e.g. AFTER INSERT
or AFTER UPDATE
etc. It does make sense to split up separate concerns into separate, small, manageable chunks of code.
The one thing you cannot rely on is that they'll be executed in a certain order - the order in which the triggers are indeed executed also doesn't have to be stable, i.e. the same every time around.