User blog comment:Ohmyn0/Making your wiki HTML5 compliant/@comment-3503487-20120705204009/@comment-957747-20120705205319

When 1.19 encounters a align="center" on a table, it replaces it with style="text-align: center" which is typically not the use for it (at least for the table itself). However, for cells,  is used often to center the text within the cell. Those instances will be converted properly.

All tables that are meant to be centered via  will have to be fixed to   instead.