Hey,
when I follow the examples to the CSS-Infection:
http://demo.vaadin.com/sampler/#foundation/cssinject
https://vaadin.com/wiki/-/wiki/Main/Dynamically%20injecting%20CSS
I see the newly added CSS-Classes (Firefox - Page Inspector)
if I add CSS-Classses multiple times, then I get multiple CSS-Classes. The browser takes the last one and everything works fine. 
Is there a possibility to delete the previous added CSS-Class?
It is not just confusing, I fear it will be too much CSS, if the websites work a long time.
For example the (old) Firebug-Extension for Firefox had some Problems with too much generated CSS-Classes.
Is there a way to prevent the accumulation of the unused CSS-Classes?
THX in advance