How to make a horizontal expandable menu fluid - html

Question

I have the following HTML code which displays a horizontal expandable menu inside a DIV:
<div id='cssmenu'>
<ul>
<li class='active'><a href='about_us.aspx'>ABOUT US</a></li>
<li>MISSION</li>
<li class='has-sub'><a href='#'>LEADERSHIP</a>
<ul>
<li><a href='#'>President</a></li>
<li><a href='#'>Medical Director</a></li>
<li><a href='#'>Board of Directors</a></li>
<li><a href='#'>Key Administrators</a></li>
</ul>
</li>
<li><a href='#'>WESTMED HISTORY</a></li>
<li><a href='#'>COMMUNITY SUPPORT</a></li>
</ul>
</div>
Here is my CSS for the menu:
#import url(http://fonts.googleapis.com/css?family=Oxygen+Mono);
#cssmenu {
padding: 0;
margin: 0;
border: 0;
width: 100%;
}
#cssmenu ul, #cssmenu li {
list-style: none;
margin: 0;
padding: 0;
}
#cssmenu ul {
position: relative;
z-index: 19;
}
#cssmenu ul li {
float: left;
min-height: 1px;
vertical-align: middle;
border-right: 1px solid #535353;
}
#cssmenu ul li:last-child {
border-right: none;
}
#cssmenu ul li.hover, #cssmenu ul li:hover {
position: relative;
z-index: 20;
cursor: default;
}
#cssmenu ul ul {
visibility: hidden;
position: absolute;
top: 100%;
left: 0;
z-index: 21;
width: 100%;
}
#cssmenu ul ul li {
float: none;
}
#cssmenu ul ul ul {
top: 0;
left: auto;
right: -99.5%;
}
#cssmenu ul li:hover > ul {
visibility: visible;
}
#cssmenu ul ul {
bottom: 0;
left: 0;
}
#cssmenu ul ul {
margin-top: 0;
}
#cssmenu ul ul li {
font-weight: normal;
}
#cssmenu a {
display: block;
line-height: 1em;
text-decoration: none;
}
#cssmenu {
background: #333;
border-bottom: 4px solid #1b9bff;
font-family: Tahoma, Arial, sans-serif;
font-size: 12px;
}
#cssmenu > ul {
*display: inline-block;
}
#cssmenu:after, #cssmenu ul:after {
content: '';
display: block;
clear: both;
}
#cssmenu a {
background: #333;
color: #CBCBCB;
padding: 0 12px;
}
#cssmenu ul {
text-transform: uppercase;
}
#cssmenu ul ul {
border-top: 4px solid #1b9bff;
text-transform: none;
min-width: 190px;
}
#cssmenu ul ul a {
background: #1b9bff;
color: #FFF;
border: 1px solid #0082e7;
border-top: 0 none;
line-height: 150%;
padding: 16px 20px;
}
#cssmenu ul ul ul {
border-top: 0 none;
}
#cssmenu ul ul li {
position: relative;
}
#cssmenu > ul > li > a {
line-height: 48px;
}
#cssmenu ul ul li:first-child > a {
border-top: 1px solid #0082e7;
}
#cssmenu ul ul li:hover > a {
background: #35a6ff;
}
#cssmenu ul ul li:last-child > a {
border-radius: 0 0 3px 3px;
box-shadow: 0 1px 0 #1b9bff;
}
#cssmenu ul ul li:last-child:hover > a {
border-radius: 0 0 0 3px;
}
#cssmenu ul ul li.has-sub > a:after {
content: '+';
position: absolute;
top: 50%;
right: 15px;
margin-top: -8px;
}
#cssmenu ul li:hover > a, #cssmenu ul li.active > a {
background: #1b9bff;
color: #FFF;
}
#cssmenu ul li.has-sub > a:after {
content: '+';
margin-left: 5px;
}
#cssmenu ul li.last ul {
left: auto;
right: 0;
}
#cssmenu ul li.last ul ul {
left: auto;
right: 99.5%;
}
For desktop and large screen it works great but whenever I load it inside a tablet the image goes over to the next line:
How can I make the menu more fluid, so it resizes based on the amount of space that's available to the cssmenu DIV?

Answer 1

Check out flexbox, this might be an option for you.
This demo is pretty handy, you would choose space-around (if I understood your question correctly): http://codepen.io/chriscoyier/pen/FAbpm