parent.location
references the same window. And I don't know where you got the ideas for the other things you tried, but window.open
seems to be what you're looking for:
<div onclick="window.open('http://google.com')" data-mce-onclick="">
<button class="button"><font size=”6”>Visit Google</font></button>
</div>
It's worth noting also that you're using very old and deprecated tags. center
and font
should be replaced with CSS styling.