opera browser shows menu (css) different online and local - css

Question

after having read many helpful hints on this side I am full of hope that I can find an answer to my problem here.
The web page I'm working on contains a horizontal menu with button background-imgs.
Testing it on browsers after validation it looks fine on FF, Chrome and Opera. After upload i discovered that online Opera does not show part of the buttons while the other browsers have no difference. ????
Thanks in advance for any ideas about this issue

Answer 1

In addition to my above mail...
trying, testing, biting my nails I discovered that the odd rendering of the menu happens only on 2 of 5 links... one named "commonmail.html" and the other linking back to the "index.html". When I choose fantasy names or just type href="#" the css is rendered properly.I added the links to 2 screenshots to show the problem:
menu with fantasy link names
menu with normal link names
The mark-up is this one:
<ul>
<li><a class="direkt" href="#">home</a></li>
</ul>
<ul>
<li class="firstlevel">our houses
<ul>
<li>in nikiti</li>
<li>in kastri</li>
<li>new projects</li>
</ul>
</li>
</ul>
<ul>
<li><a class="direkt" href="nikiti_info.html" title="Informations about Nikiti and the peninsula of Sithonia">nikiti</a></li>
</ul>
<ul>
<li class="firstlevel">informations
<ul>
<li>company</li>
<li>buying property in greece</li>
</ul>
</li>
</ul>
<ul>
<li><a class="direkt" href="commonmail.html" title="Informations about Nikiti and the peninsula of Sithonia">contact</a></li>
</ul>
</nav>
And the css is this one:
nav {
width: 704px;
padding: 0 0 0 16px;
float: left;
}
nav ul {
float: left;
width: 138px;
list-style-type: none;
}
nav li.firstlevel {
font-size: 93%;
font-weight:bold;
text-align: center;
padding-top: 17px;
padding-bottom: 17px;
color: #fff;
border: 1px solid transparent; /*--erforderlich für IE 7--*/
background: url(../pic/button110.png) 50% 50% no-repeat;
}
nav a {
text-decoration: none;
display: block;
font-size: 90%;
text-align: left;
padding-left: 6px;
padding-top: 6px;
padding-bottom: 6px;
background: url(../pic/sublistbg.png) 0 0 repeat-x;
color: #fff;
}
nav a:hover {
color: #454545;
background: url(../pic/sublisthoverbg.png) 0 0 repeat-x;
}
nav li {
position: relative;
}
nav ul ul {
position: absolute; top:50px; left: 30px;
width: 170px;
z-index: 2;
display: none;
}
nav ul li:hover ul {
display: block;
}
nav ul a.direkt:link {
font-size: 93%;
font-weight: bold;
padding-top: 17px;
padding-bottom: 17px;
padding-left: 0;
text-align: center;
color: #fff;
border: 1px solid transparent;
background: url(../pic/button110.png) 50% 50% no-repeat;
}
nav ul a.direkt:hover {
color: #454545;
background: url(../pic/button110active.png) 50% 50% no-repeat;
border: 1px solid transparent;
}