Recently active topics in PBwiki tagged with errors

When I try to attach a file, it erases my entire page. How do I prevent this?

My pbwiki has links to an external website. Sometimes when students click on those links, and then click the back button, they can't get back to the wiki. The Internet Explorer window, says page not found, website might be down or unavailable. We close IE, then try to re-open the wiki, and the page not found error is there. Tis eems to happen randomly, on different computers.