There is a system like Clickmeter that allows people to create a smart link for their banner ads. Here is a short explanation of the system. You can enter a URL as the landing page and system gives you back a special URL to put instead of the original. Now if someone clicks on the special link, he will be redirected to the landing page that you wanted to.
I am developing something like that but here is the trouble. I must use 301 redirect because of some SEO things, and 301 redirect is only available in server side as I know. But I want to get some client data such as browser name, operating system model and browser language before redirecting the client. And I am doing this part in javascript, absolutely client side.
I dont know what to do or if I am wrong about something else. But I know that Clickmeter is doing exactly the thing that I want to. They get some client data and then do 301 redirect. Here is a sample link of CLickmeter: http://9nl.it/vz0d