Eterno problema: la compativilidad IE vs FF

[TheViejo]

Hola, mira lo primero que he detectado en tu css es el uso de " (comillas), eliminalas y te funcionara en ff.

Tu css sin comillas :

Código:

.Big_contenedor{
width:400px;
height:400px;
border:5px solid;
padding:0px;
margin:0px;
}

.Div{
padding:0px;
margin:0px;
width:99%;
height:99%;
background-color:#a9d974;

}

.Div.top
{
    background-image:url('imagenes/top_line.gif');
    background-repeat:repeat-x;
    height:28px;
    width:100%;
    margin:0px;
    padding:0px;
}

.Div.top.top_izq {
    float:left;
    width:28px;
    height:28px;
    z-index:2;
    background-image:url('imagenes/top_left.gif');
    background-repeat:no-repeat;
    margin:0px;
    padding:0px;
}

.Div.top.top_der {
    float:right;
    width:28px;
    height:28px;
    z-index:3;
    background-image:url('imagenes/top_right.gif');
    background-repeat:no-repeat;
    margin:0px;
    padding:0px;
}


.Div.bottom
{
    height:28px;
    width:100%;
    z-index:1;
    background-image:url('imagenes/bottom_line.gif');
    background-repeat:repeat-x;
    margin:0px;
    padding:0px;
}

.Div.bottom.bottom_izq {
    float:left;
    width:28px;
    height:28px;
    z-index:2;
    background-image:url('imagenes/btm_left.gif');
    background-repeat:no-repeat;
    margin:0px;
    padding:0px;
}

.Div.bottom.bottom_der {
    float:right;
    width:28px;
    height:28px;
    z-index:3;
    background-image:url('imagenes/btm_right.gif');
    background-repeat:no-repeat;
    margin:0px;
    padding:0px;
}


.Div.central{
    float:right;
    width:100%;
    height:100%;
    z-index:1;
    margin:0px;
    padding:0px;
}
.Div.central.izq {
    float:left;
    width:28px;
    height:100%;
    z-index:5;
    background-image:url('imagenes/left_line.gif');
    background-repeat:repeat-y;
    margin:0px;
    padding:0px;
    position:relative;
    top:0px;
    left:0px;
}

.Div.central.der{
    float:right;
    width:28px;
    height:100%;
    z-index:4;
    background-image:url('imagenes/right_line.gif');
    background-repeat:repeat-y;
    margin:0px;
    padding:0px;
}


.Div.central.tex_box{
    width:90%;
    height:90%;
    z-index:6;
    text-align:justify;
    margin:0px;
    padding:0px;
    overflow:auto;
}
.Div.central.tex_box.h1{
    text-align:justify;
    margin:0px;
    padding:0px;
}


.Div.central.tex_box.pie{
    float:right;
    text-align:right;
    font-size:0.85em;
    width:100%;
    height:28px;
    z-index:1;
    margin:0px;
    padding:0px;
    /*border:2px solid;*/
}

Un saludo.