There's no option, but you can instruct your browser to do it. Install the Stylish extension (Chrome, Firefox). In Firefox, you can use this code:

@namespace url(http://www.w3.org/1999/xhtml);
@-moz-document domain("askubuntu.com") {
    div#custom-header {
        display:none !important;
    }
}

In Chrome, enter the following code, and specify that it applies to “URLs on the domain” askubuntu.com.

div#custom-header {
    display:none !important;
}

_{Everything you ever wanted to know about custom CSS}

There's no option, but you can instruct your browser to do it. Install the Stylish extension (Chrome, Firefox). In Firefox, you can use this code:

@namespace url(http://www.w3.org/1999/xhtml);
@-moz-document domain("askubuntu.com") {
    div#custom-header {
        display:none !important;
    }
}

In Chrome, enter the following code, and specify that it applies to “URLs on the domain” askubuntu.com.

div#custom-header {
    display:none !important;
}

_{Everything you ever wanted to know about custom CSS}