Use the ‘fieldset’ (<fieldset>...</fieldset>) element to group form data areas together!
Most browsers will display these groups with a line around the edge. This presentation of this grouping can be altered with CSS and also helps clarify data groups to users.
The legend element (<legend>...</legend>) comes directly after the fieldset element tag. The caption should help identify the purpose of this form group.
<form action="http://www.example.com/subscribe.php">
<fieldset>
<legend>Contact details</legend>
<label>Email:<br /><input type="text" name="email" /></label><br />
<label>Mobile:<br /><input type="text" name="mobile" /></label><br />
<label>Telephone:<br /><input type="text" name="telephone" /></label>
</fieldset>
</form>