You need to change the WhatPage function in order to change that text. You have to add new cases and new lang-strings in the language file that you use.
The WhatPage function is located in active_users.asp. Look for the following:
strPage = strPage & """>"
select case lcase(trim(fScript))
case "active.asp"
strPage = strPage & fLang(strLangMOD_Ls3kAU_01160)
A new page could look like this, added after the above code (if you don't want the text to be a link, remove the green-marked text):
case "classifieds.asp"
strPage = strPage & fLang(strLangMOD_Ls3kAU_01600)
Then you need to add the new lang-string to your language file (Im assuming that you are using english). The redmarked text might have to be a different number, if you have used it for something else.
strLangMOD_Ls3kAU_01600 = "Viewing classifieds"