Strange symbol in the url using Iron:router {{pathFor "somepage"}}

I’m getting this symbol, #!, every time I use the {{pathFor}} for iron router, for instance:

localhost:3000/#!datatable and in production it is the same: 3w.xxx.com/#!datatable.

Does someone knows what means? it’s very annoying and It does not say anything in the documentation http://iron-meteor.github.io/iron-router/