[Plugin: Custom CSS Manager] My CSS code disappears – why can't I see it?

I just installed the Custom CSS Manager plugin. When I first went to the plugin edit screen, it showed PHP code for echo $custom_css_code. I erased that, entered some CSS, saved it, and the CSS took affect.

But once it was saved, my CSS disappeared, and the echo statement was displayed in the editor again.

Is there a way to keep displaying the css which is in effect? Also, why does the echo statement keep reappearing? If I preface my CSS code with this persistent echo statement, my code doesn’t work.

The two lines of code I am using are:
.disappearing-next-month-coming-soon {display:inline;}
.disappearing-next-month-link {display:none;}
I am alternately toggling display of these two elements.

Thanks.

http://wordpress.org/extend/plugins/custom-css-manager-plugin/