Frequency of updates and additions
The search engines are basically trying to give their users the best possible user experience when they click on a link from their SERPs.
In order to facilitate this, the search engines assume that a site that is regularly updated and added to with new content, is more likely to be useful and relevant to that site's users.
Therefore, they give sites that are frequently updated and added to, a "boost" in their index.
The process of updating and adding to a site should be based on the content of the site and the key phrases that have been targeted for it.
For instance, the V&A site should feature regular news and information that can be seen to be of interest to students, journalists and the like. The search engine spiders will interpret regular relevant additions to the site, as an indication that the site is a valuable resource of information to those interested in "museum", "art", "design", "fashion", "photography" etc. related searches.
Additional pages being added to a site on a frequent basis are the key to this, though they should be combined with updates to existing pages on a frequent basis as well.
For example, the Photography home page
http://www.vam.ac.uk/collections/photography/index.html
should be updated with fresh content at least once a month, preferably once a week, and ideally on a daily basis. (Obviously there will be resource implications for this kind of regular updating procedure, however, which need to be taken into account).
These updates should take the form of being completely new pieces of text, graphics or interactive elements, rather than being simply a slight rewording of what existed on the page previously.
