I have the following code in my web page

<div class="RegFieldsCountry">
<ajaxToolkit:ComboBox ID="Country" runat="server" CssClass="RegComboEntry" TabIndex="8" Width="180" 
     ValidationGroup="SetUserValGroup" AppendDataBoundItems="true" DropDownStyle="DropDown" ToolTip="Country Selection" 
     BackColor="#C0C0C0" ValidateRequestMode="Enabled" EnableViewState="true" ListItemHoverCssClass="CountryHoverListItem"/>
<asp:RequiredFieldValidator ID="RequiredRegComboValidator" runat="server" ControlToValidate="Country" ErrorMessage="Η επιλογή χώρας επιβάλλεται." ToolTip="Η επιλογή χώρας επιβάλλεται." ForeColor="red" ValidationGroup="SetUserValGroup" CssClass="RequiredValidator"/>

What I get from that is a ComboBox in the exact place on page inside of a Fildset, and a Drop Down List far away in right - down of the page outside of the Fieldset.
What I need is to have the Drop Down List just below of the control.

Is there someone to assist me on this issue?

Check your CSS classes, to make sure they are not floating it over or repostioning it somehow.