syntetix
Hi
This gap can be the Padding of content. Add this code in /css/custom.css file
.t3-mainbody {
padding-top: 58px;
}
It will reduce the space, if you want to reduce it more, you can change the 58px value to a lower value.
Note : if the code does not work, I need the site URL to look on this gap style.
Regards
