mjg234 Create a single-line text field in your form, make it hidden, then add this as the default value:
{http_referer}
This should store the URL of the web page, up to the top-level domain (such as .com, .net, .edu, etc.).
If you want to store everything after the top-level domain of the URL, then create another field the same way, but use this as the default value:
{request_uri}
{http_referer} and {request_uri} are undocumented merge tags that will place the values described above into the single-line text fields when the form is submitted. Those values can seen when viewing the form entries.
I hope this helps.