Tamaño de formulario

No consigo que la anchura del formulario sea igual en Explor er que en
Firefox y Opera. ¿Cual es el problema?.

ENLACE: http://www.arkitera.es/web/contacto/contacto.htm

HTML:

<code>&lt;div class="form"&gt;
&lt;form id="myform" class="cssform" action=""&gt;

&lt;p&gt;
&lt;label for="user"&gt;Nombre&lt;/label&gt;
&lt;input type="text" id="user" value="" /&gt;
&lt;/p&gt;

&lt;p&gt;
&lt;label for="emailaddress"&gt;Correo electrónico:&lt;/label&gt;
&lt;input type="text" id="emailaddress" value="" /&gt;
&lt;/p&gt;

&lt;p&gt;
&lt;label for="comments"&gt;Asunto:&lt;/label&gt;
&lt;input type="radio" name="hobby"/&gt;
M&amp;aacute;s información sobre un proyecto&lt;br /&gt;
&lt;input type="radio" name="hobby" class="threepxfix" /&gt;
M&amp;aacute;s informacion sobre un socio &lt;br /&gt;
&lt;input type="radio" name="hobby" class="threepxfix" /&gt; Visitar un edificio
&lt;br /&gt;
&lt;input type="radio" name="hobby" class="threepxfix" /&gt; Concertar una cita
&lt;br /&gt;
&lt;/p&gt;

&lt;p&gt;
&lt;label for="comments"&gt;Comentarios:&lt;/label&gt;
&lt;textarea name="textarea" cols="25" rows="5" id="comments"&gt;&lt;/textarea&gt;
&lt;/p&gt;

&lt;div style="margin-left: 150px;"&gt;
&lt;input type="submit" value="Submit" /&gt; &lt;input type="reset" value="reset"
/&gt;
&lt;/div&gt;
&lt;/form&gt;
&lt;/div&gt;
&lt;div id="foto_contacto"&gt;
&lt;img src="estudio2.jpg" alt="Foto del estudio" /&gt;
&lt;/div&gt;

CSS:

.form{
float:left;
margin-left:37px;
}

.cssform p{
width: 425px;
clear: left;
margin: 0;
padding: 5px 0 8px 0;
padding-left: 150px; /*width of left column containing the label elements*/
border-top: 1px dashed gray;
}

.cssform label{
font-weight: bold;
float: left;
margin-left: -150px; /*width of left column*/
width: 145px; /*width of labels. Should be smaller than left column (155px)
to create some right margin*/
}

.cssform input[type="text"]{ /*width of text boxes. IE6 does not understand
this attribute*/
width: 180px;
}

.cssform textarea{
width: 250px;
height: 150px;
}

/*.threepxfix class below:
Targets IE6- ONLY. Adds 3 pixel indent for multi-line form contents.
to account for 3 pixel bug:
http://www.positioniseverything.net/explorer/threepxtest.html
*/

* html .threepxfix{
margin-left: 3px;
}

#foto_contacto{
padding-left:15px;
float:left;
}

#foto_contacto img{
width:449px;
}</code>