Electron internal css doesn´t work

I can´t style my html file with internal css. I would like to use internal because its better then inline. Inline works.

Thats my html file linking.

<link rel="stylesheet" type="text/css" href="/Tutorial/css/loginStylesheet.css">

Thats my stylesheet.

html{
background-color: #012C40;
}

body{
margin: 0px;
background-color: #012C40;
}

The window works but not the styling.