<com:TContent ID="Content">
<style type="text/css">
	.errorclassA, .errorclassB {
		background-color:pink;
	}
</style>
<com:TTextBox ID="A" />
<com:TRequiredFieldValidator ControlToValidate="A" Text="Required!" ControlCssClass="errorclassA" ValidationGroup="A"/>
<com:TEmailAddressValidator ControlToValidate="A" Text="No Email!" ControlCssClass="errorclassA" ValidationGroup="A"/>
<com:TButton Text="Click" ValidationGroup="A" />

<br />

<com:TTextBox ID="B" />
<com:TRequiredFieldValidator ControlToValidate="B" Text="Required!" ControlCssClass="errorclassB" 
        ValidationGroup="B" EnableClientScript="False" />
<com:TEmailAddressValidator ControlToValidate="B" Text="No Email!" ControlCssClass="errorclassB" 
    ValidationGroup="B" EnableClientScript="False" />
<com:TButton Text="Click" ValidationGroup="B" />

</com:TContent>