Q: how to go back to previous app?

Let's say i'm surfing the web with safary app.

At a certain point i click a link that fires up a new app (for example youtube or maps).

How may I go back to the previous safary instance?

If i go home and then into safary again, then safary will start from the main page rather than the page that provided the link to the external app. This is very irritating as it seems the previous view is lost forever.