[TheLastSuperman]

Then your default style must be from the original 4.x version or a past 4.x default version i.e. if you installed 4.2.1, it installed a default 4.2.1 theme and if you're on 4.2.3, even if it said the templates and such merged correctly it is not in fact a 100% Default 4.2.3 style, follow? That could be your case I'm not sure.

This will work-around the default style issue, add this to additional.css:

.body_wrapper {
margin-top:-10px !important;
}

Edit: I was still typing Seven . Use Seven's method above, it uses !important like mine but his brain said "let's set the above body to 0" which is better than setting the body_wrapper to -10, so use his respectively!