This article describes how to make a web control or user control invisible on the web page, but still reside in the HTML Document Object Model (DOM).
<asp:button id="TimeAdd" runat="server" style="display: none;visibility: hidden;" text="Submit">
You'll notice that the Button web control doesn't have a style attribute. ASP.NET will pass the attribute and value to the browser "as-is". The resulting HTML is: