By default the main menu / category menu is set to float left, depending on your website template you may want to center the categories of this menu.
To do so, edit your themes stylesheet.css and change:
#menu ul {
list-style: none;
margin: 0;
padding: 0;
}
To:
#menu ul {
list-style: none;
margin: 0 auto;
padding: 0;
display: table;
}
Save, and upload
