html, body, div, span, applet, object, iframe,
h1, h2, h3, h4, h5, h6, p, blockquote, pre,
a, abbr, acronym, address, big, cite, code,
del, dfn, em, img, ins, kbd, q, s, samp,
small, strike, strong, sub, sup, tt, var,
b, u, i, center,
dl, dt, dd, ol, ul, li,
fieldset, form, label, legend,
table, caption, tbody, tfoot, thead, tr, th, td,
article, aside, canvas, details, embed,
figure, figcaption, footer, header, hgroup,
menu, nav, output, ruby, section, summary,
time, mark, audio, video {
margin: 0;
padding: 0;
border: 0;
font-size: 100%;
font: inherit;
vertical-align: baseline;
}
html {
box-sizing: border-box;
}
*, *:before, *:after {
box-sizing: inherit;
}
.container {
margin:0 auto;
width:80%;
}
body {margin:0;}
ul {
list-style-type: none;
margin: 0;
padding: 0;
//overflow: hidden;
position: fixed;
top: 0;
width: 80%; /*QUA CERA 100% E NON ANDAVA BENE. XKE? XKE QUANDO ES FIXED THEN THE width reference to the document and not his parent. QUINDI FACEVA RIFERIMENTO AL 100% DEL DOCUMENTO, NON DEL PADRE (CONTAINER). QUINDI METENDOLA A 80% GLI DICIAMO DI PRENDERE L'80% DEL TOTALE, DEL DOCUMENTO, CHE E' QUELLO CHE VOLGIAMO PER LA NOSTRA UL*/
}
li {
float: left;
font-weight: bold;
}
li a {
display: block;
color: black;
text-align: center;
padding: 14px 16px;
text-decoration: none;
}
li a:hover:not(.active) {
background-color: #111;
}
.imgheader {
text-align: center;
padding-top: 0.5%;
}
.navheader{
border: 1px solid rgba(0, 0, 0, 0.3);
height: 50px;
}
.buttonheader1 {
margin: 10px;
padding: 8px 10px;
background-color: #6288A5;
border: 1px solid #4D7B9F;
border-radius: 3px;
color: #fff ;
margin-right: 80px;
clear:both;
}
.buttonheader2 {
margin: 10px;
padding: 8px 10px;
background-color: #6288A5;
border: 1px solid #4D7B9F;
border-radius: 3px;
color: #fff ;
clear:both;
}
.buttonleft{
margin: 10px;
padding: 8px 10px;
background-color: white;
border: 1px solid #4D7B9F;
border-radius: 3px;
color: black;
font-weight: bold;
position:relative;
right:20%;
}
<body>
<div class="container">
<div class="nav">
<div class = "navheader">
<div class="leftheader">
<ul>
<li style="float:left"><button class="buttonleft" type="button">SECTIONS</button></li>
<li style="float:left"><a href="#home">HOME</a></li>
<li style="float:left"><a href="#news">SEARCH</a></li>
</ul>
</div>
<div class="rightheader">
<ul>
<li style="float:right"><button class="buttonheader1" type="button">LOG IN</button></li>
<li style="float:right"><button class="buttonheader2" type="button">SUBSCRIBE</button></li>
</ul>
</div>
<div class="imgheader">
<img src="logo.png" alt="logo">
</div>
</div>
<div class="navarticles">
</div>
</div>
<div class="content">
</div>
<div class="footer">
</div>
</div>
</body>