When the calendar widget is activated in the sidebar, it generates the following validation error (W3C markup validation):
The summary attribute is obsolete. Consider describing the structure of the table in a caption element or in a figure element containing the table; or, simplify the structure of the table so that no description is needed.
…alendar</h3><div id="calendar_wrap"><table id="wp-calendar" summary="Calendar">
How can I rectify this without messing with any core file?
Working with WP3.1.4, twentyten theme.