Hi earthbeheard and welcome to the forum!,
the problem with those links is that the destination isn't correct because
http://earthbeheard.page.tl/loss.of.oil ,
http://earthbeheard.page.tl/loss.of.water ,
http://earthbeheard.page.tl/global.warming and
http://earthbeheard.page.tl/2010 were never created, so you can't link them before doing that.
What you gotta do is add those pages in your "Manage pages" option. Once you create them you'll see their links at the the top of the page, alongside the confirmation message:
Image:
That's the URL (link) you want to use in your hyperlinks.
If you have any other question we'll be here to help you
Have fun!
