It’s not in your stylesheet. Look at the view-source of that page. Line 258 the rule is there (CTRL+F for the font-size)
.header-mobile__bottom .mobile-menu li a, .header-mobile__bottom .mobile-menu ul > li > ul.children ,nav.primary-navigation > ul li a, nav.primary-navigation > ul > li > ul.children, header .search-container .search-holder, .main-header .cosmo-social li a{ font-size:10px !important; font-family: "gotham HTF" !important; font-weight:normal; font-style:inherit; }
Not a problem! I assume you were looking at the inspect element of Chrome (firebug for FF?). Eithre way, on the right pane, where you see the declarations and rules, you can see at the top right section of each box, it says where the code came from. Go revisit and see!