I’ve been using a lot of bootstrap features on my website (ASP.NET) and they all work fine.
But when I add a button it looks funny:

This is the tag:
<asp:Button ID="btnCheck" runat="server" Text="Bla" CssClass="btn btn-success" OnClick="btnCheck_Click" />
FF looks weird as well:

I made sure that all the links to the bootstrap.css and bootstrap.js are OK.
Any ideas?
Well, it seems I used an old version of bootstrap and it was updated to 2.1.1 , I downloaded the new version and everything looks good. Thanks for the help!