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Instead of using the error message &quot;Error&quot; I would like to change the textbox txtzipcode&nbsp; background red using CSS can this be done.<br />
<br />
&lt;form id=&quot;form1&quot; runat=&quot;server&quot;&gt;<br />
&nbsp; &nbsp; &lt;div&gt;<br />
&nbsp; &nbsp; <br />
&nbsp; &nbsp; &nbsp; &nbsp; &lt;asp:TextBox ID=&quot;txtzipcode&quot; runat=&quot;server&quot;&gt;&lt;/asp:TextB<wbr />ox&gt;<br />
&nbsp; &nbsp; &nbsp; &nbsp; &lt;asp:RegularExpressionVali<wbr />dator ID=&quot;ValZipcode&quot; runat=&quot;server&quot; <br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; BorderStyle=&quot;None&quot; ControlToValidate=&quot;txtzipc<wbr />ode&quot; <br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; ErrorMessage=&quot;Error&quot;<br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; <br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; <br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; ValidationExpression=&quot;^((\<wbr />d{5}-\d{4}<wbr />)|(\d{5})|<wbr />([AaBbCcEe<wbr />GgHhJjKkLl<wbr />MmNnPpRrSs<wbr />TtVvXxYy]\<wbr />d[A-Za-z]\<wbr />s?\d[A-Za-<wbr />z]\d))$&quot; <br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; ForeColor=&quot;#FF3300&quot;&gt;&lt;/asp:<wbr />RegularExp<wbr />ressionVal<wbr />idator&gt;<br />
&nbsp; &nbsp; &nbsp; &nbsp; &lt;br /&gt;<br />
&nbsp; &nbsp; &nbsp; &nbsp; &lt;asp:Button ID=&quot;Button1&quot; runat=&quot;server&quot; Text=&quot;Button&quot; /&gt;<br />
&nbsp; &nbsp; <br />
&nbsp; &nbsp; &lt;/div&gt;<br />
&nbsp; &nbsp; &lt;/form&gt;
</div>
</div>


Instead of using the error message "Error" I would like to change the textbox txtzipcode  background red using CSS can this be done.

<form id="form1" runat="server">
    <div>
    
        <asp:TextBox ID="txtzipcode" runat="server"></asp:TextBox>
        <asp:RegularExpressionValidator ID="ValZipcode" runat="server" 
            BorderStyle="None" ControlToValidate="txtzipcode" 
            ErrorMessage="Error"
            
            
            ValidationExpression="^((\d{5}-\d{4})|(\d{5})|([AaBbCcEeGgHhJjKkLlMmNnPpRrSsTtVvXxYy]\d[A-Za-z]\s?\d[A-Za-z]\d))$" 
            ForeColor="#FF3300"></asp:RegularExpressionValidator>
        <br />
        <asp:Button ID="Button1" runat="server" Text="Button" />
    
    </div>
    </form>

How to change the textbox background color when the Regular expression shows an error?Bookmark:Question:

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