Which page is referring to *all posts by author*?

please refer to the codex:
http://codex.wordpress.org/Template_Hierarchy#Author_display

however, your problem is caused by a conflict of the .author class output by the body_class() and this existing style in custom.css:

.author {
    float: left;
    margin-top: -3px;
    width: 219px;
    background: #E7ECEF;
    border-right: 1px solid #D6DFDC;
    height: 41px;
    cursor: pointer;
}

check why this style is added there in the first place;
if there is no reason, remove it;
if there is a good reason, try to change it to:

#content .author { ......