For my last question, I found this code :
margin: 0 auto;
padding: 10px 0px;
border-top: 0px solid rgba(0,0,0,.1);
In this exemple, when I change the margin parameter to 20px, it’s okey because it created a border at the top of the header but there ‘s a problem with the picture image background : it exceed the right edge of the header). How could I do ?
But for the first questions : How can Imake round the corners ? maybe with something like “radius-border” but I have not find the CSS code again, could you help me ?