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<form method="post" action="dump.php">
    <textarea name="content">
    <h2>The below class on the iframe element is stripped out by the editor</h2>
    <iframe class="test" width="425" height="350" src="https://maps.google.co.uk/?ie=UTF8&amp;t=m&amp;ll=52.8382,-2.327815&amp;spn=4.646012,9.338379&amp;z=6&amp;output=embed"></iframe>
    <p>I want to be able to add a class to iframe elements in order to select them with CSS. Use the HTML view to see that the class attribute isn't there in the editor. This fiddle is for <a href="http://stackoverflow.com/questions/13161323/tinymce-strips-class-attribute-from-iframe-element">this stack overflow question.</a></p>
</textarea>
</form>