Found a bug in WordPress

On http://www.crenext.com/seo, there is the following code:

<a href="http://www.crenext.com/seo/#Introduction">Introduction - I am new to SEO.</a>

<a href="http://www.crenext.com/seo/#Intermediate">Intermediate - I know what SEO is but I need to learn.</a>

<a href="http://www.crenext.com/seo/#Advanced">Advanced - Tell me advanced techniques.</a>

<h3 id="Introduction">Introduction</h3>

When I clicked on “Preview Changes” in WordPress 4.1.1 and test the link for “Introduction”, “Intermediate”, or “Advanced”, then the link goes to the saved page instead of the link where the id is. So while I can preview changes, I cannot test the internal link. It could be an additional feature for WordPress users or a bug.