Хорошо, удалили его и заново создали с более ясными (я надеюсь) классами, которые теперь отлично работают во всех браузерах.CSS:
fieldset
{margin: 1em 0;набивка: 1em;граница: 0px solid #ccc;фон: # 000;}
legend {font-weight: bold;преобразование текста: верхний регистр;}
label.label {display: block;плыть налево;ширина: 10em;}
textarea {width: 157px;высота: 125 пикселей;цвет фона: # 000;граница: 1px solid #fff;цвет: #fff;размер шрифта: 90,9%;семейство шрифтов: Arial;}
select.birthday {width: 52px;цвет фона: # 000;граница: 1px solid #fff;цвет: #fff;размер шрифта: 90,9%;}
select.ddl {width: 162px;цвет фона: # 000;граница: 1px solid #fff;цвет: #fff;размер шрифта: 90,9%;}
input [type = "text"] {width: 160px;цвет фона: # 000;граница: 1px solid #fff;цвет: #fff;размер шрифта: 90,9%;}
.right-input {width: 100%;выравнивание текста: справа;}
Форма:
<asp:UpdatePanel ID="upEnquiryForm" runat="server">
<ContentTemplate>
<fieldset>
<legend class="no-display">Hello</legend>
<p>
<label class="label" for="txtFirstName">Name</label>
<asp:TextBox ID="txtFirstName" ValidationGroup="RegForm" MaxLength="25" runat="server"></asp:TextBox>
<asp:RequiredFieldValidator ID="rfvName" ControlToValidate="txtFirstName" Text="*" CssClass="validation-error"
Display="Dynamic" ValidationGroup="RegForm" runat="server"></asp:RequiredFieldValidator>
</p>
<p>
<label class="label" for="txtLastName">Name</label>
<asp:TextBox ID="txtLastName" ValidationGroup="RegForm" MaxLength="25" runat="server"></asp:TextBox>
<asp:RequiredFieldValidator ID="rfvLastName" ControlToValidate="txtLastName" Text="*" CssClass="validation-error"
Display="Dynamic" ValidationGroup="RegForm" runat="server"></asp:RequiredFieldValidator>
</p>
<p>
<label class="label" for="txtEmail">Email</label>
<asp:TextBox ID="txtEmail" ValidationGroup="RegForm" MaxLength="50" runat="server"></asp:TextBox>
<asp:RequiredFieldValidator ID="rfvEmail" ControlToValidate="txtEmail" Text="*" CssClass="validation-error"
Display="Dynamic" ValidationGroup="RegForm" runat="server"></asp:RequiredFieldValidator>
<asp:RegularExpressionValidator ID="revEmail" ControlToValidate="txtEmail" Text="*" CssClass="validation-error"
Display="Dynamic" ValidationExpression="^[\w-]+(\.[\w-]+)*@([a-z0-9-]+(\.[a-z0-9-]+)*?\.[a-z]{2,6}|(\d{1,3}\.){3}\d{1,3})(:\d{4})?$"
ValidationGroup="RegForm" runat="server"></asp:RegularExpressionValidator>
</p>
<p>
<label class="label" for="txtPostcode">Postcode</label>
<asp:TextBox ID="txtPostcode" ValidationGroup="RegForm" MaxLength="10" runat="server"></asp:TextBox>
<asp:RequiredFieldValidator ID="rfvPostcode" ControlToValidate="txtPostcode" Text="*" CssClass="validation-error"
Display="Dynamic" ValidationGroup="RegForm" runat="server"></asp:RequiredFieldValidator>
</p>
<p>
<label class="label" for="txtBirthday">Birthday</label>
<asp:DropDownList ID="ddlDay" ValidationGroup="RegForm" AppendDataBoundItems="true" CssClass="birthday" runat="server">
<asp:ListItem Text="--" Value="0"></asp:ListItem>
</asp:DropDownList>
<asp:DropDownList ID="ddlMonth" ValidationGroup="RegForm" CssClass="birthday" runat="server">
<asp:ListItem Text="--" Value="0"></asp:ListItem>
</asp:DropDownList>
<asp:DropDownList ID="ddlYear" ValidationGroup="RegForm" CssClass="birthday" runat="server">
<asp:ListItem Text="--" Value="0"></asp:ListItem>
</asp:DropDownList>
</p>
<p>
<label class="label" for="gender">Gender</label>
<asp:DropDownList ID="Gender" CssClass="ddl" runat="server">
<asp:ListItem Text="-- select --" Value="Did not say"></asp:ListItem>
<asp:ListItem Text="Male" Value="Male"></asp:ListItem>
<asp:ListItem Text="Female" Value="Female"></asp:ListItem>
</asp:DropDownList>
</p>
<p>
<label class="label" for="iam">I am</label>
<asp:DropDownList ID="Iam" CssClass="ddl" runat="server">
<asp:ListItem Text="-- select --" Value="Did not say"></asp:ListItem>
<asp:ListItem Text="Straight" Value="Straight"></asp:ListItem>
<asp:ListItem Text="Gay Male" Value="Gay Male"></asp:ListItem>
<asp:ListItem Text="Lesbian" Value="Lesbian"></asp:ListItem>
<asp:ListItem Text="Trans Gender" Value="Trans Gender"></asp:ListItem>
<asp:ListItem Text="Bisexual" Value="Bisexual"></asp:ListItem>
<asp:ListItem Text="Queer" Value="Queer"></asp:ListItem>
<asp:ListItem Text="Do not want to disclose" Value="Do not want to disclose"></asp:ListItem>
</asp:DropDownList>
</p>
<p>
<label class="label" for="txtMobile">Mobile</label>
<asp:TextBox ID="txtMobile" ValidationGroup="RegForm" MaxLength="12" runat="server"></asp:TextBox>
</p>
<p>
<label class="label" for="txtEnquiry">Enquiry</label>
<asp:TextBox ID="txtEnquiry" ValidationGroup="RegForm" TextMode="MultiLine" Rows="5" Columns="10" runat="server"></asp:TextBox>
</p>
<p class="right-input">
I agree to the <a id="termsandconditions" href="Terms.htm">terms & conditions</a>
<asp:CheckBox ID="chkAgreeTerms" ValidationGroup="RegForm" CssClass="checkbox" runat="server" />
</p>
<p class="right-input">
Receive the latest offers by email<asp:CheckBox ID="chkAgreeEmail" Checked="true" CssClass="checkbox" runat="server" />
</p>
<p class="right-input">
Receive the latest offers by SMS<asp:CheckBox ID="chkAgreeSMS" Checked="true" CssClass="checkbox" runat="server" />
</p>
<p class="right-input">
<asp:ImageButton ID="imbSubmit" ImageUrl="~/images/forms/submit-button.png" ValidationGroup="RegForm"
OnClick="imbSubmit_Click" CssClass="submit" runat="server" />
<asp:ImageButton ID="imbSkip" ImageUrl="~/images/forms/skip-button.png" OnClick="imbSkip_Click"
CssClass="submit" runat="server" />
</p>
<p>
<asp:Label ID="lblMessage" runat="server"></asp:Label>
</p>
</fieldset>
</ContentTemplate>
</asp:UpdatePanel>
Спасибо всем, кто помог.