Show or hide outline data in MS Excel 2010

If you don't see the outline symbols one two three, plus, and minus, click the Microsoft Office Button Button image, click Excel Options, click the Advanced category, and then under the Display for this worksheet section, select the worksheet, and select the Show outline symbols if an outline is applied check box.

Ref: http://office.microsoft.com/en-us/excel-help/outline-group-data-in-a-worksheet-HA010095247.aspx#BMshow_or_hide_outlined_data