Blank Cells

Using GoToSpecial

Highlight the cells containing all the cells, including the blank cells.
(Home tab, Editing Group)(Find & Select - GoTo Special) or (F5, Special).
This will display the "Go To Special" dialog box.
Select Blanks and press OK.
This will select all the cells that are blank.

Using Find Dialog

Highlight the cells containing all the cells, including the blank cells.
(Home tab, Editing Group)(Find & Select - Find) or (Shift + F5).
This will display the "Find and Replace" dialog box.
Leave the "Find What" box blank and press "Find All".
Select (Ctrl + A) to select all the occurrences and press OK.
This will select all the cells that are blank.