Double posting with a possible automated solution. It would probably need a bit of ironing out; if it would even work at all. I still think a manual instruction solution is better.
You can set and read cookies with HTACCESS; therefore what you could do is something like this:
Use HTACCESS to check whether a cookie ("has_used_private_browsing") exists when they type your domain name; if the cookie is present, browse as normal; if the cookie does not exist; assume this is a first visit and direct them to a discreet page via a URL shortner. Before you do this, set a short life cookie ("show_private_browsing").
The page that the URL shortner loads will read that short life "show_private_browsing" cookie; if its valid; show a "private browsing" instruction (discreet, no branding) with a continue when you have done this link; which sets a cookie ("has_used_private_browsing") before forwarding them to the website. If the short life cookie has expired, forward them to somewhere benign so the short URL looks like it was for somewhere else and don't show the private browsing message.
Also, add exceptions to the HTACCESS to search engines don't get caught up.
The question would be; whether within that process, the initial domain name the user typed would enter into the history if you were to redirect straight to the URL shortner; I am not sure off hand.
@FizixRichard The solution that I posted (i really don't know if it works, as i didn't test) is supposed to only wipe the page itself from the history, not the whole history. But I agree that an explanation on how to do it would be more educative and clear.
I read it as deleting all the browsing history, but my point remains that I would not rely on it as it could offer a false sense of security; heck I would not rely on my solution above if it worked as you could interfere with some browsers or firewalls; even lock visitors out.
The best solution is advising about private browsing and how to delete individual history entries for each of the major browsers; as abusers of all kinds tend to be devious and intelligent. So they could find out (i.e. from the cookies). Also if you auto delete the entries and the user is clued up (as they live with an abuser they are probably well aware that they need to be careful) the fact that there are no entries there could spook them and cause them distress; leaving them wondering if there is a trace or not; which would nag them.
ETA: MikeChipShop raises a good point with telling the user how to delete a single site from history. It might actually be worth just showing a popup giving instructions on how to delete individual pages from history manually.
Remember, someone coming from google is going to have the search query in their history; like "Google Search: Domestic violence support".
So when they are done, they could clear their tracks only for the specific sites they want to hide away without clearing everything and alerting their abuser to the fact they have "done something" they could get attacked for.
Edited by FizixRichard, 09 October 2012 - 04:01 PM.