Chapter 10. The Form API, Page 225

Location on the page: 
Section "Looking for a Validation Function" (first paragraph on page)
Chapter: 
10. The Form API
Error: 

A validation function for a form can be assigned by setting the #validate property in the form to an array with the function name as the key and an array as the value. Anything that appears in the latter array will be passed to the function when it is called. Multiple validators may be defined in this way:

Correction: 

A validation function for a form can be assigned by setting the #validate property in the form to an array with the function name as the value. Multiple validators may be defined in this way:

Description of the Error: 

In Drupal 6.x, the #validate property only specifies the name(s) of the validate handler(s). The syntax in which arguments for the validate handler are defined within the #validate property applies to Drupal 5.x.