I'm facing an issue with my responsive menu. While it works perfectly on desktop browsers, it behaves strangely on mobile browsers when I try to expand the sub-menu of the menu. After scrolling up and down, the menu tends to disappear.
<style>
*{margin:0;padding:0;text-decoration:none}
body{background:#555;}
header{position:relative;width:100%;background:#333;}
.logo{position:relative;z-index:123;padding:10px;font:18px verdana;color:#6DDB07;float:left;width:15%}
...
</script>
</head>
<body>
</body>
<header>
<nav id='cssmenu'>
...
</nav>
</header>