I'm trying to prevent container collapse using

section.main::after {
    clear: both;
    content: "";
    display: table;
}

When I preview my page, the container has not opened up. Inspection shows the code being changed to

section.main::after {
    clear: both;
    content: "
    display: table;
}

I've tried changing the "" to none, but that doesn't work either. Is there a way to get around this?