How to insert strings containing slashes with sed?

A very useful but lesser-known fact about sed is that the familiar s/foo/bar/ command can use any punctuation, not only slashes. A common alternative is s@foo@bar@, from which it becomes obvious how to solve your problem.

The s command can use any character as a delimiter; whatever character comes after the s is used. I was brought up to use a #. Like so:

s#?page=one&#/page/one#g

The easiest way would be to use a different delimiter in your search/replace lines, e.g.:

s:?page=one&:pageone:g

You can use any character as a delimiter that's not part of either string. Or, you could escape it with a backslash:

s/\//foo/

Which would replace / with foo. You'd want to use the escaped backslash in cases where you don't know what characters might occur in the replacement strings (if they are shell variables, for example).