After reading the riddle, you might think "source", but that is not the answer. Combined with the clue in the title, "View" (the only one that is capitalized), you are supposed to view the source code of the page. You will find a hidden message after the problem text:
Every river starts and ends,
In between, it curves and bends.
The ends are each a mighty force,
One called Mouth and the other called
< a href="You found it! Replace BLANK with a word that rhymes with pie and begins with a capital letter! Type the following for your solution">< /a >
< a href="I found the solution as easy as pie">< /a >
< a href="One called Mouth and the other called BLANK">< /a >
Any solution of this form will work, for instance:
I found the solution as easy as pie
One called Mouth and the other called Sly.
If you're having trouble finding it, a convenient way to find the text hidden among the HTML jumble is to search the page. In Mozilla Firefox and Internet Explorer, it's CTRL-F. You could search for "river", or any other word(s) of the problem text.