Open a web page when you're using a web browser, or something else, like a text?
If it happens when you're using a web browser, install another browser, like
Firefox. If it's happening in another kind of app, not a web browser, check your default apps (without knowing the phone and version of Android, I can't tell you where to look - and if you're going to post them,
please register an account here so you can continue the conversation here, instead of starting a new one every time you post). It's not "preferences", it's the default app used for web browsing, and evidently you don't have one set.