The prompt box lets the user to enter information. The advantage of using a prompt are fairly restricted and the use of forms would frequently be preferred (from a user perspective).
The prompt box title text cannot be altered and the same applies to button text. You can have two lines of text by using \n where the new line begin (please note that the opera browser up to version 7 will display 1 line of text only)
The text entry field is same to a form input type="text". The two buttons are OK & Cancel. The value returned is either the text entered or null.
The syntax for the prompt is following
prompt("your message",""); (script tags omitted)
"your message","" the,"" holds the default text value "" = empty.