I think the strong
element is an appropriate element for such messages.
You could use several strong
elements to indicate the importance of the message:
<strong>Login successfully.</strong> <!-- confirmation -->
<strong><strong>Wrong login data.</strong></strong> <!-- warning/error -->
If it’s stand-alone message for which a heading is warranted, use a section
element instead of a div
. In case of serious errors that apply to the whole page, it should be the first element on the page.
Various variants are possible:
<section class="message message-error">
<h1><strong><strong>Error:</strong> Wrong login data.</strong></h1>
<p>The username and/or password is wrong. Try …</p>
</section>
<section class="message message-error">
<h1>Error</h1>
<p><strong><strong>Wrong login data.</strong></strong></p>
<p>The username and/or password is wrong. Try …</p>
</section>
<section class="message message-error">
<strong><strong>Wrong login data.</strong></strong>
</section>
<section class="message message-error">
<p><strong><strong>Wrong login data.</strong></strong> Try …</p>
</section>
Which one to use depends on the kind of message, if the exact error is know, if additional help text is provided, and if several message could come up at the same time.
Note that you probably don't want to use a heading for messages that apply to a single input
element (e.g. when the user didn't fill out a required field or entered wrong content etc.), as these error messages should be in the corresponding label
or directly next to the input
element.
For accessibility, you should have a look at WAI-ARIA. Maybe aria-live="assertive"
might be an appropriate way to mark error messages.