"mainContentOfPage" is a property of WebPage, and its type is
WebPageElement. So the markup is as:
<span itemprop="mainContentOfPage" itemscope
...
</span>
It need be an item scope to represent a property which is neither
a URL nor text.
"significantLinks" is a property of WebPage, and it can contain
more than one links. Each link in significantLinks is a URL. So,
on what in your examples,
lives.com/bipolar-online-test.html">bipolar online test </a>,"
it's wrong that the content of the span tag is treated as a value of
significantLinks. The correct markup is
<span>
...
<a itemprop="significantLinks" href="...">...</a>
...
<span>
On anchor tag, the value of href attribute is treated as the value
if an itemprop attribute attends and it's not a new item scope.
/yhh