I am trying to link another page to my Awareness page but everytime I click on it the error 404 pops up. The url I am trying to link it to is: http://rjheath.bravehost.com/breastcancer.html

What am I doing wrong?

Well, the main thing you are doing wrong is the hostile script that pops up messages when someone uses the context menu on your page. You should remove that before inviting anyone to look at your page.

The reason your LINK does not work, is because it goes to:
http://rjheath.bravehost.com/breastcancer.html/
it should go to
http://rjheath.bravehost.com/breastcancer.html

The closing slash tells the visitor's browser to look for a folder not a file.