El tema de las dos clases lo he solucionado dejando solo una. Gracias por la aclaración.
 
Respecto al otro tema, sí que tengo algún elemento con float. A ver si me deja poner el código.
El atributo 'float' está al final del código CSS. 
Éste es el formulario:  
Código:
 <!-- ows_prompt operator's data HTML code -->
<div id="ows_ovrl" style="display: none;"> </div>
<div id="ows_ww" style="display: none;">
	<div id="ows_win">
		<div id="ows_w">
			<div id="ows_container">
				<p><div align="right"><label class="mandatory">* <atleap:message key="tenders.operator.form.mandatoryFields"/></label></div></p>
				<p><span id="lbText" style="text-align:justify; ">
					<atleap:message key="tenders.operator.form.disclaimerText1"/>
					<a href="<atleap:content identifier="disclaimer_url"/>" target="_blank"><atleap:message key="tenders.operator.form.disclaimer"/></a>
					<atleap:message key="tenders.operator.form.disclaimerText2"/>
				</span><br /><br /></p>
				<table cellpadding="0" cellspacing="0">
				<form name="economicOperatorApplicationForm" method="post" action="/ows/econoperator/save.do" id="applicationForm">
					<input type="hidden" name="resourceId" id="resourceId" value="<%=request.getParameter("id")%>" />
					<tr>
						<td><label class="mandatory">* </label><label><atleap:message key="tenders.operator.form.name"/>:</label></td>
						<td colspan="3"><input type="text" class="w_long" id="txtName" name="name" onKeyPress="if((event.keyCode==10)||(event.keyCode==13)) ows_clk(1); if (event.keyCode==27) ows_clk(0);"></td>
					</tr>
					<tr>
						<td><label class="mandatory">* </label><label><atleap:message key="tenders.operator.form.company"/>:</label></td>
						<td colspan="3"><input type="text" class="w_long" id="txtCompany" name="company" onKeyPress="if((event.keyCode==10)||(event.keyCode==13)) ows_clk(1); if (event.keyCode==27) ows_clk(0);"></td>
					</tr>
					<tr>
						<td><label class="mandatory">* </label><label><atleap:message key="tenders.operator.form.address"/>:</label></td>
						<td colspan="3"><input type="text" class="w_long" id="txtAddress" name="address" onKeyPress="if((event.keyCode==10)||(event.keyCode==13)) ows_clk(1); if (event.keyCode==27) ows_clk(0);"></td>
					</tr>
					<tr>
						<td><label class="mandatory">* </label><label><atleap:message key="tenders.operator.form.cp"/>:</label></td>
						<td colspan="3"><input type="text" class="w_long" id="txtCP" name="postalCode" onKeyPress="if((event.keyCode==10)||(event.keyCode==13)) ows_clk(1); if (event.keyCode==27) ows_clk(0);" onkeydown="return onlyFiveDigits(event);"></td>
					</tr>
					<tr>
						<td><label class="mandatory">* </label><label><atleap:message key="tenders.operator.form.city"/>:</label></td>
						<td colspan="3"><input type="text" class="w_long" id="txtCity" name="city" onKeyPress="if((event.keyCode==10)||(event.keyCode==13)) ows_clk(1); if (event.keyCode==27) ows_clk(0);"></td>
					</tr>
					<tr>
						<td><label class="mandatory">* </label><label><atleap:message key="tenders.operator.form.country"/>:</label></td>
						<td colspan="3">
							<%
								// obtain countries' names if language changes
								String countriesLang = (String)(session.getAttribute("countriesLang"));
								String lang = ((java.util.Locale)(request.getSession().getAttribute("org.apache.struts.action.LOCALE"))).getLanguage();
								if (countriesLang == null || countriesLang != lang) { %>
									<atleap:messageSet key="ows.country" var="countries" scope="session"/>
							<%		session.setAttribute("countriesLang", lang);
								}
							%>
							<select name="country" id="selectCountry">
								<atleap:iterator var="country" items="${countries}" >
									<option value="${country.key}">${country.value}</option>
								</atleap:iterator>
							</select>
						</td>
					</tr>
					<tr>
						<td><label class="mandatory">* </label><label><atleap:message key="tenders.operator.form.phone"/>:</label></td>
						<td><input type="text" class="w_short" id="txtPhone" name="phone" onKeyPress="return isNumberKey(event);if((event.keyCode==10)||(event.keyCode==13)) ows_clk(1); if (event.keyCode==27) ows_clk(0);"></td>
						<td><label class="mandatory">* </label><label><atleap:message key="tenders.operator.form.fax"/>:</label></td>
						<td><input type="text" class="w_short" id="txtFax" name="fax" onKeyPress="return isNumberKey(event);if((event.keyCode==10)||(event.keyCode==13)) ows_clk(1); if (event.keyCode==27) ows_clk(0);"></td>
					</tr>
					<tr>
						<td><label class="mandatory">* </label><label><atleap:message key="tenders.operator.form.emailAddress"/>:</label></td>
						<td colspan="3"><input type="text" class="w_long" id="txtEmail" name="email" onKeyPress="if((event.keyCode==10)||(event.keyCode==13)) ows_clk(1); if (event.keyCode==27) ows_clk(0);"></td>
					</tr>
					<tr id="errorRow" class="mandatory">
						<td></td>
						<td colspan="3"><!-- <label class="mandatory" id="labelError"> -->
							<atleap:messages invert="true" />
						<!-- </label> -->
						</td>
					</tr>
					<tr>
						<td> </td>
						<td colspan="3">
							<input type="button" class="btn_short" id="ows_ok" onclick="ows_clk(1);" value="OK">
							<input type="button" class="btn_short" id="ows_cancel" onclick="ows_clk(0);" value="Cancel">
							<input type="button" class="btn_short" id="ows_clear" onclick="ows_clk(2);" value="Clear">
						</td>
					</tr>
				</form>						
				</table>
				<p><div align="right"><a href="<atleap:content identifier="disclaimer_url"/>" target="_blank"><atleap:message key="tenders.operator.form.disclaimer"/></a></div></p>
			</div> <!-- // ows_container -->
		</div> <!-- // ows_win -->
	</div> <!-- // ows_ww -->
</div> <!-- // ows_ovrl -->
<!-- // ows_prompt operator's data HTML code -->
  Éste el código CSS:  
Código:
 /* CSS Document with modifications for Call for Tender*/
#ows_ovrl {
background-color: black;
-moz-opacity: .4; opacity: .4;
top: 0; left: 0; position: fixed;
width: 100%; height:100%; z-index: 99;
}
#ows_ww 	{ position: fixed; z-index: 100; top: 0; left: 0; width: 100%; height: 100%; text-align: center;}
#ows_win 	{ margin: 10% 0 auto 35%; width: 400px; text-align: left;}
#ows_w 		{background-color: white; padding: 3px; border: 2px solid black; background-color: #EEE;}
#ows_t 		{color: white; margin: 0 0 2px 3px; font-family: Arial, sans-serif; font-size: 10pt;}
#ows_w span {font-family: Arial, sans-serif; font-size: 10pt;}
#ows_w div 	{margin:10px 10px 10px 10px;}
#ows_w table				{width:100%;}
#ows_w table input.w_short	{width:75px; background-color:#FFFFFF !important;}
#ows_w table input.w_long	{width:100%; background-color:#FFFFFF !important;}
#ows_w select				{width:101%; background-color:#FFFFFF !important;}
#ows_w table,
#ows_w table tr,
#ows_w table td	{background-color:#EEE; border-color:#EEE;}
#ows_ovrl a		{color:#016394;}
#ows_w a		{color:#016394;}
/*#ows_container	select, input	{background-color:#FFFFFF !important;}*/
#ows_container	input.btn_short	{width: 75px;}
.mandatory			{color:#990000;}
/* These styles override oami_website.css stylesheet (otherwise, in IE, operator's data form appears badly */
#Main form			{padding:0; float:none; margin-bottom:0;}
#Main form label	{float:left; width:auto; background:#EEE; padding:0;}
  ¿Cómo podría influir 'float' para que no se viera el texto? 
Muchas, muchas gracias por la ayuda.