I am making a website for someone and I want it to resize itself depending on the screen resolution and the zoom of the browser(I am not including smartphones). I currently have a menu wich is like that :

every element in the menu is in a div and here is the css:
#barre_utilisateur //For the menu bar(the red bar)
{
height:45px;
background-color:#A31E39;
width:100%;
}
#content_boutton_accueil //the home button
{
margin-left:2%;
width:200px;
display:inline-block;
}
#notification //exclamation mark button
{
cursor:pointer;
width:60px;
height:45px;
display:inline-block;
}
and now, I want the cogwheel icon the stick on the right on the left of the user button. I don’t see how I can achieve this.
Also, when I zoom in too much the righ part of the menu get out of where it is supposed to be is there a way to prevent this?
A good example of what I am trying to achieve is the new outlook live page
You can position the overall menu div (#barre_utilisateur) relatively, and then its children absolutely in it. For example:
Another way could be to have 2 divs inside the menu (#barre_utilisateur), and then to float the first one to the left and the other – to the right.