HTML5 Guidelines for Web Developers

58 Chapter 3—Intelligent Forms

Figure 3.12 shows what will happen if you submit the form in the preceding list-

ing without specifying an e-mail address. Opera displays the error message: This

is a required field. If you have set the Opera user interface to another language,

the error message appears in the relevant language. Of course, you can also adapt

these error messages with JavaScript; more on this in section 3.4.3.

Figure 3.12 Error message for a blank input field with the “required” attribute (Opera)

But that is not all: The field is defined as the type email, so Opera also returns an

error message if an invalid e-mail address is entered; for example, Please enter a

valid email address (see Figure 3.13).

Figure 3.13 Error message in Opera after entering an invalid e-mail address