Slider is only showing all images underneath each other

Hello,

I’ve installed the plugin, added the shortcodes and published two slides. After returning to the homepage, the slides are there, but don’t hover above each other. They are shown on top of each other.

What did I do wrong? Is it a CSS issue or something else?

I’ll be pleased if someone has the answer for me.

Thanks in advance.

http://wordpress.org/plugins/flexslider-hg/