error in formula

Giganews Newsgroups
Subject: error in formula
Posted by:  Jeff@nospam.invalid (Jeff@nospam.invalid)
Date: Mon, 17 Jan 2011

Using Excel 2007 and working on a xls file I am trying to count the
occurrences of a certain value (in this case "1940 Census") in a column.
I tried to follow the example in the XL Help and used this formula:

=SUM(IF((L2:L303="1940 Census"),1,0))

but the result I get is
and the error info says "a value used in the formula is the wrong type"

The column L2-L303 contains either blank cells, or "1940 Census", or
just words like "immigration", "History", etc.

Can someone suggest how I should correct this formula?

I also want the formula to ignore case