You don't need to worry about whatever the Data box shows, as that's disabled with the Custom option.
Note: You must enter the data validation formula for cell A2 first, then copy A2 to A3: A10 so that the second argument to the COUNTIF will match the current cell.
Check out this video for a quick data validation overview.
You can download an example workbook with all of the data validation examples you'll find in this article.
If this response does not properly escape or reject HTML control characters, a cross-site scripting flaw will ensue.
A reflected attack is typically delivered via email or a neutral web site.
Microsoft security-engineers introduced the term "cross-site scripting" in January 2000.Because HTML documents have a flat, serial structure that mixes control statements, formatting, and the actual content, any non-validated user-supplied data included in the resulting page without proper HTML encoding, may lead to markup injection.A classic example of a potential vector is a site search engine: if one searches for a string, the search string will typically be redisplayed verbatim on the result page to indicate what was searched for.You can follow along, or create your own data validation scenarios.Download Excel data validation examples Now, instead of typing your list values in the data validation Source box, you add the name that you just defined, preceded by an Equal (=) sign.