As you can see right now, it is well placed. But i've tried on some other computer and the placement is different. Is there somewhere i can found the standard Header size from salesforce by screen size?
My actual CSS is :
position: -webkit-sticky; /* Safari */ position: sticky; background-color: rgba(247, 244, 244, 0.9); top: 5.5rem; z-index:10;
Thanks everyone, Louis du Beux
FYI : i've tried this topics but i need a pure css solution that's why i'm asking for header size by window size : Sticky Header in Custom Lightning Page Template Component?