Faced with described problem:

http://jekyllrb.com/docs/upgrading/
All page and post URLs contain leading slashes
If you use the method described above, please remember that the URLs for all posts and pages contain a leading slash. Therefore, concatenating the site baseurl and the post/page url wheresite.baseurl = /andpost.url = /2013/06/05/my-fun-post/will result in two leading slashes, which will break links. It is thus suggested that prefixing withsite.baseurlonly be used when thebaseurlis something other than the default of/.