When an experiment is Google-hosted, the data for that experiment is stored on Google servers and downloaded to the webpage you are testing every time a user views your test page. Self-hosting is an alternative to Google-hosting where experiment data is embedded in the web page you are testing, removing the need to contact Google servers in order to display your page. While Google-hosting is easy to install and maintain, self-hosting requires more work and technical ability to install, but will decrease your site's dependence on Google servers and slightly improve the time it takes for your web site to display.
We recommend Google-hosting your experiment, but you should understand the following factors if you want to consider self-hosting:
Ease of setup
Setting up a web site for Google-hosting is fairly easy, requiring only that the site be edited with Website Optimizer tags once. Setting up a web site for self-hosting requires significantly more technical involvement involving periodically fetching the latest experiment data from Google servers, storing it somewhere in your system, and dynamically embedding it in your test page.
Potential delays
With Google-hosting, your page must retrieve data from Google servers before displaying anything, introducing a small delay of perhaps 1/10 of a second. With self-hosting, all experiment data is stored in your page. This increases the size of your page (especially if you have a lot of or large content variations), but doesn't require the page to connect to Google server, ultimately resulting is a smaller delays.
Google dependency
With Google hosting, there's the chance that if Google servers experience problems (highly unlikely, since we use some stellar servers), your page may take a while to render, waiting for a timeout for the Google server resource. With self-hosting, you don't have this dependency -- as long as you can serve out your pages, they will render normally. Note that in either case, because the default content is always in your page, your web site will always render properly.
