When I recently spoke at Cambridge, I took this photo at King's College.
Wikipedia has this to say, in general...
The window tax was a property tax based on the number of windows in a house. It was a significant social, cultural, and architectural force in England, France and Scotland during the 18th and 19th centuries. To avoid the tax some houses from the period can be seen to have bricked-up window-spaces (ready to be glazed or reglazed at a later date), as a result of the tax. It was introduced in 1696 and was repealed in 1851, 156 years after first being introduced. Spain and France both had window taxes as well for similar reasons.
Update: Here's a recent paper on the window tax, brought to my attention by the authors.
The Window Tax (Working Paper) A Case Study in Excess Burden
Author(s): Schwab, Robert M. and Wallace E. Oates
Publication Date: April 2014