Yes, you are misunderstanding him. Those two images at the top right of your site are *not* related to the <link> tag in the <head> portion of the page.
In your case, you need to look lower down the page, where this code is:
<div id="hdrimg">
<span class="validation">
<a href=""><img src="http://alternapop.com/wp-content/themes/fluidity3c-10/images/rss.gif" alt="Subscribe to RSS" /></a>
<a href=""><img src="http://alternapop.com/wp-content/themes/fluidity3c-10/images/rsscomments.gif" alt="Subscribe to Comments" /></a>
</span>
The href's are empty. That's why those links are broken. Find where those href's are generated in your template (probably at the bottom of header.php) and fix them there.
As for your original question, 'rss2_url' is a hardcoded parameter for the bloginfo() function. You can find other possible parameters here:
http://codex.wordpress.org/Template_Tags/bloginfo