Problemas con Divs..

[IsaBelM]

haz estos cambios

<div id="menu_cont"><nav>
<ul id="menu">
<li id="menu_active"><a href="index.php?id=0">Inicio</a></li><li><a href="index.php?id=1">Quien somos</a></li><li><a href="index.php?id=2">Proyectos</a></li><li class="bg_none"><a href="index.php?id=3">Contacto</a></li>
</ul>
</nav></div>

#menu_cont {
top: -30px;
position: relative;
z-index: 1;
border-color: #BEBEBE;
border-bottom-left-radius: 18px;
border-bottom-right-radius: 18px;
border-style: none solid solid solid;
border-width: 0 1px 1px 1px;
}

#logo_box {
background: #2C2D2E;
padding: 38px 0 22px 0px;
border-radius: 18px;
-moz-border-radius: 18px;
-webkit-border-radius: 18px;
box-shadow: 0 1px 3px #b7b7b7;
-moz-box-shadow: 0 1px 3px #b7b7b7;
-webkit-box-shadow: 0 1px 3px #b7b7b7;
behavior: url(js/PIE.htc);
z-index: 2;
margin-top: -18px;
width: 100%;
overflow: hidden;
}

header nav {
background: url(../images/menu_bg.gif) bottom repeat-x;
padding-top: 36px;
height: 47px;
behavior: url(js/PIE.htc);
padding-left: 10px;
}


.text1 {
font-size: 36px;
color: #545454;
line-height: 48px;
letter-spacing: -2px;
}

elimina los selectores

header, #page1 #logo_box, #page1 header nav, #page1 .text1