Webpages are optimizing through the use of experiments that compare the responses of viewers that are either presented with the original webpage or a variant thereof. One or more variants are first defined through the use of a browser-based editor application that initially examines the webpage for a snippet of code. The snippet can be added to the webpage, if missing, and the webpage returned to the editor application. Changes made to the webpage to define a variant are saved in variation code. When the webpage is later requested by multiple viewers, in each instance the viewer receives the webpage with the snippet, the snippet instructs the browser to download a file, and the instructions of the file determine whether the viewer will see the variant or the original webpage. Tracking viewer responses to the webpage and the variant allow a statistical basis for comparison to be developed.