When HTML5 autocomplete is on, the browser will automatically complete values that the user has entered before.
This HTML5 autocomplete attribute works with the following input types: text, search, url, tel, email, password, datepickers, range, and color.
Also you can turn off this autocomplete attribute by using this attribute autocomplete="off"
[php]
<form action="/" autocomplete="on">
First name:<input type="text" name="f_name" />
E-mail: <input type="email" name="email" autocomplete="off" />
<input type="submit" />
</form>
[/php]
On this above HTML form autocomplete on and autocomplete is off for email input field.