Method 1: Filling Blanks via a Formula
Say you have a list of entries in column A similar to previous Figure, and within the list you have many blank cells. Here is a quick and easy way to fill those blanks with the values of the cells above them.
Select all the data in column A, and then select Home → Editing → Find & Select → Go To Special (pre-2007, Edit → Go To...or hit Ctrl-G and choose Special). Check the Blanks option and click OK. At this point, you have selected only the empty cells within the list. Press the equals key (=), then the up arrow key. Holding down the Ctrl key, press Enter.
You can quickly convert formulas to values only by selecting column A in its entirety. Right-click and select Copy (Ctrl-C), right-click again and select Paste Special..., check the Values checkbox, and then click OK.