Css hover dropdown list - html

Question

i creat a dropdown list when mouse hover at #clim the height of #dropdown change from 0 to 150px . but the code not work .
html code
<div id="menu">
<ul>
<li id="index">Accueil</li>
<li id="clim">Climatisation</li>
<li id="ventil">Ventilation</li>
<li id="electro">Electromenager</li>
</ul>
</div>
</div>
<div id="dropdown" >
<ul>
<li id="index">Climatisation</li>
<li id="clim">Ventilation</li>
</ul>
</div>
CSS code
#dropdown{
margin-left:693px;
width:165px;
height:0px;
position:absolute;
background:#158DFB;
overflow:hidden;
-webkit-transition-duration:0.3s;
}
i have a problem in this part . not working
#clim:hover #dropdown{
height:150px;
}

Answer 1

first of all, your code has extra finishing tags and 2 elements with the same id (#clim), that doesn't make the question very clear.
to make this work with css and no javascript you have to include the hidden element (the dropdown) inside the outer element that you will hover and trigger the dropdown to be shown.
try this instead and then add the remaining css rules you need:
<div id="menu">
<ul>
<li id="one">Accueil</li>
<li id="two">
Climatisation
<ul id="dropdown">
<li id="subone">sub Link</li>
<li id="subtwo">Another sub link</li>
</ul>
</li>
<li id="three">Ventilation</li>
<li id="four">Electromenager</li>
</ul>
</div>
#dropdown{
height: 0;
overflow:hidden;
-webkit-transition-duration:0.3s;
}
#menu:hover #dropdown{
height:150px;
}

Answer 2

when mouse hover at #clim the height of #dropdown change
You cannot do that with pure CSS, because there is no parent selector.