I haven't used J2MEPolish, but I assume you refer to the same thing described in this
J2ME Polish TableItem Documentation.
It appears that you can give one or more CSS attributes (described on the TableItem documentation page) to a markup class or id. These styles would then be applied to the table cells with the same markup class or id.
I looked into the API and found the
colspan attribute described in the
de.enough.polish.ui.FakeCustomItem class.
colspan: when this item is embedded in a table, you can span it over several cells, e.g. colspan: 2;.
In terms of table cells the colspan integer describes how many cells, in the horizontal direction, the styled cell would span.