You should use Paint.NET, it's very friendly too and super easy to make things transparent.
I actually use paint tool sai, but really wouldn't recommend it haha :) its not very pixel friendly, i just like how easy it is to use. then i run it through this to make it transparent http://www.online-image-editor.com
What editor do you use?
didnt notice that, sorry! i'll fix it up soon :)
You've got some pixels that aren't transparent when they should be in the strings.