given transcript across a set of strains or individuals. At the same time, the amount of data contained in many views has grown, for example the increased number of species has greatly added to the data presented in views containing comparative genome information. It is not straightforward to identify bottlenecks for users in web based systems. For example, analysing web log files does not easily distinguish between web pages which are of interest to a limited number of users and pages which most users have not discovered. Perceived web site performance can also be very different for different users as a result of different browsers, desktop machines and network speeds. Since the last report (14) considerable effort has been invested in understanding and addressing these issues, culminating in a substantially redesigned and reengineered website from Ensembl release 51 (November 2008).
