Create a group box around certain controls on a web form using CSS

A fieldset with a legend provides a visual and semantic grouping for form controls. You can then style this as desired with CSS. A fieldset is somewhat unique in that the legend is capable of visually interrupting the border of its parent fieldset (possible with other elements, but difficult).

Example: http://jsfiddle.net/NUMcr/1/

<fieldset>
<legend>Group 1</legend>
    <input type="text" />
    <asp:Textbox runat="Server" id="txt1" />
    <!-- etc -->
</fieldset>

fieldset {
    margin: 8px;
    border: 1px solid silver;
    padding: 8px;    
    border-radius: 4px;
}

legend {
    padding: 2px;    
}