These dialogs are expected to respect the settings and preferences of the user in the web browser (and operating system), such as default font-size, colors, and language.
In addition to providing instructions, validate user input to help users avoid mistakes.
HTML5 defines a range of built-in functionality to validate common types of input, such as email addresses and dates.
In some situations, such as validating custom controls or supporting legacy browsers, additional scripting may be necessary to validate user input.
Custom validation needs to notify users in an accessible way as described in the User Notifications part of this tutorial.
Client-side validation alone does not ensure security; therefore data needs to be validated on the server-side as well.
Forms frequently include required input that needs to be clearly identified using labels.In addition, the attribute can be added to form controls, to programmatically indicate that they are required.Most current web browsers support this attribute and will communicate missing required input to the user, using standard web browser dialog mechanisms.Note that the label also displays “(required)”, to inform users that don’t use assistive technology or use older web browsers that do not support the HTML5 attribute informs assistive technologies about required controls so that they are appropriately announced to the users (as opposed to validating the input).Most current web browsers automatically set its value to .Most current web browsers support these features and handle input validation.