Hi ! I don´t understand why my div class="footer" doesnt appear, everthing else seems to work fine. Thx for help !

<!DOCTYPE html>
<html>
<head>
    <title>Hauptseite</title>
    <meta http-equiv="Content-Type" content="text/html; charset="UTF-8">
<style type="text/css">
 html,body{height:100%;margin:0;background-color:#191970;}
.maincontent{position:relative;min-height:100%;margin-left:10%;margin-right:10%;background-image:url(pic1_pixabay.jpg);background-size:100%;background-repeat: no-repeat;}
.frontbox{position:absolute;margin-top:1%;left:1%;right:2%; padding:20px;font-size;text-align:center;background-color:white;opacity:0.5;border:thick solid #4D94FF;border:(255, 255, 255, .5); border-radius: 25px;}
.sidebox{position:absolute;top:40%;left:2%;width: 250px;background-color:white;opacity:0.5;border:thick solid #4D94FF;border-radius: 25px;}
.footer{background-color:black;}
</style>
</head>
<body>
<div class="maincontent">
<div class="frontbox">
 <a href="UnserePhilosophie.html">Unsere Philosophie</a>&nbsp
 <a href="url">&Uumlber uns</a>&nbsp 
 <a href="url">Unser Portfolio</a>&nbsp 
 <a href="url">Blog</a>&nbsp 
 <a href="url">Unser Kontakt</a>&nbsp 
 <a href="url">Sample Page</a>&nbsp 
 <a href="url">Tryout Page</a> 
</div>
<div class="sidebox">
 <ul style="list-style-type:disc">
 <li><h1>Updates und Archive</h1></li>
 <li><a href="url">J&aumlnner 2015</a></li>
 <li><a href="url">Februar 2015</a></li>
 <li><a href="url">M&aumlrz 2015</a></li>
 <li><a href="url">April 2015</a></li>
 <li><a href="url">Mai 2015</a></li> 
 <li><a href="url">Archive</a></li> 
 </ul>

</div>
<div class="footer"> Impressum  all rights reserved </div>
</div>
</body>
</html>

html5 :: no type on css or script

line 9 querying border:thick solid #4D94FF;border:(255, 255, 255, .5); duplicate definitions
and ;font-size; no size

for .footer{background-color:black;}
try .footer{background:black;color:white;position:fixed;bottom:0;z-index:1;}
to;
stick the div in place,
make other elements slide under as they scroll
give contrast between background and text

you can condense css
background-image:url(pic1_pixabay.jpg);background-size:100%;background-repeat: no-repeat;}
is the same as background:url(pic1_pixabay.jpg) 100% no-repeat;}

when you get it all right for this page,
put the script and css to external files, used for all pages
makes every page smaller and faster

Hello and good luck,