Test:sandbox
<!DOCTYPE html PUBLIC> <html>
<body>
<iframe frameborder="0" scrolling="no" href="Source of text (easy)" name="iframe" id="iframe">
Error message
</iframe>
<a href="Source of text (easy)" target="iframe">Short explanation</a>
<a href="Source of text (hard)" target="iframe">Detailed explanation</a>
</body>
</html>