Need help in the process of creating your own WordPress theme?
Here are some restrictions to keep in mind:
attrparameter from Post Options first level
boxcontainers, is not used. Because boxes are added with add_meta_box() which has no parameter for specifying attributes.
There are no restrictions for what options are contained in the
options parameter. It’s possible to create multi level options: boxes inside boxes, tabs inside boxes, tabs inside tabs, and so on.