Styling Standard Images with CSS doesn't work

Hi togehter,

I would like to style an image I added to a text-block with the css-class function. I’m using Enfold as a child theme. So first I entered the class name “ownpic” at the picture-details area on the field “css-class”. After saving it I entered the following code to my style.css:

.ownpic img {
border: 0px !important;
background: transparent !important;
}

But the picture does not change styles, background stays white. I tried .gif and also .png files. At the advanced layer slider the picture is correctly shown with a transparent background. Other styles don’t work too, like e.g.

.ownpic img {
border: 10px !important;
}

I also tried

.ownpic {
border: 0px !important;
background: transparent !important;
}

and

img .ownpic {
border: 0px !important;
background: transparent !important;
}

But all these codes won’t work. What did I do wrong?

Greetings, Andreas