I found out what seems to be the problem, but unfortunately I could not find any solution yet. Maybe you can find out what goes wrong in this code:
#site-logo {
float: right;
height: 110px;
width: 930px;
}
#site-logo img {
height: 110px;
max-height: 110px;
width: 720px;
float: right;
}
#hgroup {
float: right;
width: 100%;
text-align: right;
}
#header-left {
width: 100%;
float: left;
}
Thanks for already helping me out with the mobile menu issue.