Basically, you want the logo between the left corner and the text image. To achieve perfect symmetry, you need to change your markup. Change the html to this :
<div id="logo">
<a href="index.html"><img src="img/logo.png" height="80" width="214"></img></a>
<a href="storitve.html"><img src="img/Napis.png" height="80" width="448"></img></a>
<div id="FB_GPlus_logo">
<a href="http://www.facebook.com/5ekdoo" target="_blank">
<img src="img/Facebook_Logo.png" width="40px" height="40px"></img>
</a>
</div>
</div>
Now select all the elements inside the #logo div and make them all float left and with a proportional width
#logo > a, FB_GPLUS_logo {
float : left;
width:33%;
min-height:80px;
text-align:center;
}
This should create three divs with a width of 33% thereby almost occupying the header and all the content in the divs will be center aligned. As a last point, because all the elements are floats you may need to apply this '.clearfix' class to the parent div in which all theses three divs reside.
.clearfix:after {
content :'';
clear:both;
display:block;
}