Fixed invalid em value, thanks @mokolabs

Author: gseguin

css/structure/jquery.mobile.core.css

@@ -45,7 +45,7 @@ div.ui-mobile-viewport { overflow-x: hidden; }
 .ui-bar h1, .ui-bar h2, .ui-bar h3, .ui-bar h4, .ui-bar h5, .ui-bar h6 { margin: 0; padding: 0; font-size: 16px; display: inline-block; }
 
 .ui-header, .ui-footer { position: relative; overflow: hidden; width: 100%; border-left-width: 0; border-right-width: 0; }
-.ui-header .ui-btn-left { position: absolute; left: 10px; top: .em;  }
+.ui-header .ui-btn-left { position: absolute; left: 10px; top: .4em;  }
 .ui-header .ui-btn-right { position: absolute; right: 10px; top: .4em; }
 .ui-header .ui-title, .ui-footer .ui-title { min-height: 1.1em; text-align: center; font-size: 16px; display: block; margin: .6em 30% .8em;  padding: 0;  text-overflow: ellipsis; overflow: hidden; white-space: nowrap; outline: 0 !important; }
 .ui-footer .ui-title { margin: .6em 15px .8em;  }