What does this mean?

Each page should have a well defined page title (as defined by a single <title> tag).

98.4% done

How close this website is to fixing this issue.

HTML Found on page Issues
<head></head> 1
<head><link id="mylinkid" href="/css/invalid.css" rel="stylesheet"></head> 1
2 distinct issues were found in the sample of 126 web pages.
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