Toggle menu doesn't work

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CSS

HTML

jQuery

Hey there, I am trying to build a responsive Website. I've never used the @media tag before, so I am not sure if I did anything wrong.

The nav should be a slidetoggle menu when the window size is smaller than 550px.

It works when I decrease the browser window, but not on my iPhone. I want the nav changing to the toggle at 550px and the header height changing to the toggle height (2em).

I hope you can help me.

HTML:

<meta name="viewport" content"width=device-width, initial-scale=1.0, maximum-scale=1.0, user-scalable=no">


<div id="header">
    <section id="menubar">
        <ul>
            <li><a class="menubutton" href="#menu"><img src="images/menu.png" /></a></li>
        </ul>
    </section>
        <nav class="nav">
            <ul>
                <li><a href="test.html">test</a></li>
                <li><a href="test.html">test</a></li>
                <li><a href="test.html">test</a></li>
                <li><a href="test.html">test</a></li>
                <li><a href="test.html">test</a></li>
            </ul>
        </nav>
</div>

The css:

ul {
margin:0px;
padding:0px; }

li {
list-style:square;
font-weight:100;
color:#000000;
line-height:1em;
padding:0em; }

a {text-decoration: none; }

div#header {
position: fixed;
height: 6.250em;
width: 100%;
background-color: #fff;
top: 0;
z-index: 999; }

#menubar {
display:block;
background:#ffffff; }

#menubar ul {
display:block;
width:2em;
padding:0.9em; }

#menubar ul li {
display:inline; }

#menubar ul li a.menubutton {
display:none; }

#menubar img {
width:90%;
height:auto;
max-width:100%; }

nav ul {
display:block;
position: absolute;
left: 15%;
bottom: 0.625em;
font-size: 0.875em; }

nav ul li {
display:inline;
margin:0em 0.625em 0em 0em; }

nav ul li a {
color:#000; }

nav ul li a:hover {
color:#cc9900; }

nav ul li a.active {
color:#cc9900; }

@media screen and (min-width:600px) {
nav.nav {
    display:block !important;
}
}

@media screen and (max-width:550px) {
#menubar ul li a.menubutton {
    display:block;
}   
nav {
    display:none;
    height:auto;
}
nav ul li {
    display:block;
    margin:0.2em 0em 0.2em 0em;
}
}

@media screen and (max-width:550px) {
div#header {
height: 2em !important;
}

@media screen and (max-width:550px) {
div#content {
top: 2em !important;
}

What I have tried:

I've changed the max-widths, but still on the iphone it looks always like the fullsize in the browser.
I changed the header size for the toggle nav, but it never worked properly like a simple drop down toggle (like this one here http://slicknav.com/)