myrrh - 6:48 pm on Jan 4, 2013 (gmt 0)

When a select list in a form shows by default an instruction such as "Select" or "Month" (in the drop-down list itself, not text above the drop-down box), what is that called?

For example, if I have a drop-down list of the months of the year and I want the list to display the word "Month" by default (and not be a submitted value), what is that function called?