The Previous page is kind of vague, and may depend on how the website is made.
The Back arrow in Safari will take you to the last visited address. Wether that's your last page is not certain.
Some websites do not have physical page changes so nothing to go back to. They change the content of the same page.
To store favorites or Bookmarks, tap on the twisted arrow icon that's on the left side of the address bar. Then tap on Bookmark.
When you want to access the favorites, tap on the little book icon to the left of the twisted arrow, and tap on the bookmarks tab if its not selected and then tap on the link you want to open.