Some site tile changed into other page's link without watching this page.
Some pages I added to "Site tile" were often changed into other pages. For example "Google News"( https://news.google.co.jp/ ). I added this page to "Site tile". But the link of tile of this page was often changed into other page's link ( http://www.google.co.jp/s/chuspo/article/2014042801002383.html ) without watching this page! And my blog ( http://kyu3.blog.jp/ ). The link of tile of my blog was often changed into other page's link ( http://blog.jp/ )! So, I hope that these changed page would to become easily the original added page by some way! (For example, If I delete history and chache (and so on) of Coast, these changed page would to become the original added page. ) I hope the function like it.
The tiles in Coast are not bookmarks to specific sites, but instead to Web Apps.
To add specific sites to your home screen, you can do like we recommended here:
Hope this helps!