An earlier project (VB6, ASP 3.0) I worked in used HTC files to add custom attributes and methods to the HTML controls. This allowed us to define a text box with custom attributes. e.g. if I define a textbox with attribute Ctype = "Date", then the onblur() event would automatically verify whether the text entered is a date and so on. With the advent of ASP.NET, is it still a common practice to use HTC files or there is another way to achieve this sort of flexibility? One way I can think of is to add custom attributes on page load event and then add appropriate event-handlers. Please explain.