In this case, not really a philosophical question, but one of relevance to web browsing.
HTTP provides a value “referer”, which is the URL of the page from which the current request originated.
In ASP, this value can be retrieved with Request.ServerVariables(“HTTP_Referer”).
See this W3Schools page for details.
Here are a couple of code snippets to illustrate:
for each x in Request.ServerVariables response.write(x & "<br>") next response.write Request.ServerVariables("HTTP_REFERER")