Cause: The workbook contains one or more sparklines, which cannot be displayed in earlier versions of Excel.
Solution: To maintain compatibility with earlier versions, remove sparklines and use a chart or conditional formatting to illustrate trends in the data.
Click a sparkline.
On the Sparklines tab, under Edit, click the arrow next to Clear, and then click Clear Selected Sparkline Groups
Repeat this step to remove all remaining sparklines.
Note: Even if you choose not to replace the sparklines in this workbook, they remain available and are applied when the workbook is opened again in Excel for Mac 2011 or Excel 2010 for Windows, unless another user saves the workbook in an earlier file format, such as .xls.