Just stumbled onto this when visiting a local planning application website. The site plans were all in Tiff format which of course cannot be easily viewed in a browser.
The site directed you to an Alternative tiff viewer at Alternative tiff viewer
Its easy to install for both Internet explorer and other browers including Mozilla Firefox, and its free. You do however have to register.
I found it very useful, particularly as otherwise when clicking on the image to be viewed the brower went to Paint Shop pro my image program and was slower and much more difficult to view!
Take a look.
Hazel