How do you delete a remotes/origin/{branch}?
use: git remote prune origin
or use git remote prune origin --dry-run
to preview what branches will be removed.
As in git help remote
prune
Deletes all stale remote-tracking branches under . These stale branches have already been removed from the remote repository referenced by , but are still locally available in "remotes/".
With --dry-run option, report what branches will be pruned, but do not actually prune them.
git push origin :[branch-name]
.
Source: http://progit.org/book/ch3-5.html
I suggest you have a look at http://www.git-tower.com/
It's a great GUI for GIT