[teh_klev]

Not sure why you're being downvoted. Many of the sibling comments are referring to server side generated HTTP 302 headers, and server side (without lots of fancy shenanigans) you won't know (server side) if the client has disabled scripting on the first page hit.

And document.location is pointless if the client has turned off scripting.

[aendruk]

Different readings of the initial question:

A) “how do people redirect”, to which the point about noscript sounds like irrelevant whining

B) “how do people redirect only visitors who don’t have scripting” to which most of the answers are trivially wrong