line colour

Hey guys,

I expect that this is ridiculously basic but I wanted to leave a space between between my slider and my header.

I tried
which didn’t work and then <hr> which left a sufficient space, however I don’t want to be able to see the line. I tried adding;

hr {
height:1px;
background-color:#FFFFFFF;
border:0;
}

To the CSS however it didn’t take. Does anybody know of anything else that I can try?

Thanks ??