Adding the Option Explicit line to an ASP file that is scripted in VB Script forces you to declare each of the variables that you use within your VB Script on your page. This option helps prevent typos in variable names by forcing your code to be more structured. This has long been a standard practice in Visual Basic, but in Visual InterDev, it tends to be ignored because Visual InterDev does not automatically add this line to your ASP pages. This, of course, is by design in Visual InterDev because not all ASP pages are scripted in VB Script.
If you want to automatically include <%Option Explicit%> in your new ASP pages in Visual InterDev 6, you can simply add it to your new ASP template file by editing the file with an editor such as NotePad. You can find this file within your Visual InterDev Templates folder usually in this location: C:\Program Files\Microsoft Visual Studio\VIntDev98\Templates\NewFileItems\New ASP Page.asp. Make sure to add the line right after the <%@Language=VBScript%> line.
This file is a template file, so other preferences can also be set in this file, such as adding default comment headers and copyright information.