TheExcelAddict.com
Microsoft Excel "Quick Tips"

Select All Cells On A Worksheet

Whenever you need to make a change (i.e. column widths, row heights, etc...) that will affect the whole worksheet, a quick way to do it is by clicking on the small gray square at the intersection of the row and column labels (i.e. immediately to the left of the A in column A). This will highlight all the cells in your worksheet.

As always, it's a good idea to also know a keyboard shortcut. In versions of Excel prior to 2003, pressing CTRL+A will select all cells.

In Excel 2003, things have changed. If the worksheet contains data and you select a cell or cells containing data, pressing CTRL+A will select the only Current Region. To select all cells, you will need to press CTRL+A a second time.