You can use ActiveX controls in any Visual Basic application, including those that run over the Internet. However, there are some special considerations when creating controls for use over the Internet.
Digital Signature All executable components should bear a "digital signature" identifying the author and certifying that they are safe to run and safe to use in scripts. You can get a digital signature from VeriSign (http://www.verisign.com) or other vendors for a fee.
Threading Model ActiveX controls must use a threading model that is compatible with their host application. Single-threaded applications can use controls with either single threading or apartment threading, but apartment-threaded applications can only use apartment-threaded controls. DHTML applications are apartment threaded.
Asynchronous Loading By default, all objects load asynchronously over the Internet. You need to be careful that objects are initialized before you refer to them in code. Use the IsNull function to see if an object exists before referring to it.
Packaged for Distribution ActiveX controls installed over the Internet must have a setup program to install them. The easiest way to do this is to use the Package and Deployment Wizard to create the necessary .CAB and .HTM files. See Chapter 9, "Creating Internet Applications," for information about using the Package and Deployment Wizard to create Internet setup programs.
The Asynchronous Animation control created in Chapter 6, "ActiveX Controls," is designed for use over the Internet. The following sections use that control in HTML, DHTML, and ActiveX document components in each of their samples, which can be found on the companion CD-ROM.