Banner file's height can start around 200~250 pixels up to 400. (more is overkill and wastes too much real estate)
Adjust the jpg compression accordingly. (higher if your banner doesn’t contain much contrasted details or texts)
Check out /s/testsub and resize your browser's window to see the banner adapting to it.
You can use the following code for your sub.
.subbanner { background-color: #000; display:grid; margin:auto; position: relative; top:0px; width: 66vw !important; height: 13.5vw; background-size: 100% !important; background: url(%%poalbanner%%) no-repeat;
}
.subbannerm { background-color: #000 !important; background: url(%%poalbanner%%) no-repeat center/contain; height: 4.05em; width: 100%; margin-bottom: -0.1em; margin-top: -0.3em;}
.submenumargin { padding-top: 3em !important; }
(post is archived)