CSS ineffective

Hello
After some trials with different themes, this custom CSS does not work anymore (
I want to remove the logo in the header of the homepage.) :

body.home #site-logo {
    display: none;
}

I have removed everything belonging to the previous themes, including in the hoster files. I have tried removing and downloading my logo again, and thousand other trials since yesterday. I have emptied the cache of my browser. Nothing works. I have also activated WPSupercache only after the problem showed, and emptied it.
NB : if I remove my own logo, the theme’s name appears.
I am a beginner and I don’t know how to go further. Can you please help me ?
Thanks in advance.