1. Method for A/B testing or multivariate testing of a website on a computer being connected to a web content management system; the web content management system comprising: storage means for storing website content data in the form of content objects and for storing one or more website variants, wherein a website variant defines a structure of one or more webpages of a website on the basis of stored content objects, and rendering means for creating markup language representation data of one or more webpages on the basis of a website variant and content objects indicated by the website variant; the method comprising: receiving, at the web content management system from a requesting computer, a webpage data request directed to a webpage of a website for which at least two website variants including a first website variant and a second website variant are defined, and selecting one website variant of the at least two website variants of the website; wherein: if the first website variant is selected, the method further comprises: creating, at the web content management system, first markup language representation data of the webpage on the basis of the first website variant and content objects indicated by the first website variant, and providing the requesting computer with the first markup language representation data of the webpage; and if the second website variant is selected, the method further comprises: creating, at the web content management system, first markup language representation data of the webpage on the basis of the first website variant and content objects indicated by the first website variant, creating, at the web content management system, second markup language representation data of the webpage on the basis of the second website variant of the website and content objects indicated by the second website variant, determining, at the web content management system, differences between the created first and second markup language representations of the webpage, creating, at the web content management system, webpage difference data on the basis of the determined differences, the created webpage difference data indicating the differences between the first and second markup language representation data of the webpage, providing the requesting computer with the first markup language representation data of the webpage, and providing the requesting computer with the created webpage difference data for post-processing of the first markup language representation at the requesting computer on the basis of the webpage difference data.