Userscripts allow you to run scripts on websites loaded into your browser. This allows you to modify pages to your likings and use modifications written by others.
I wrote a userscript converting that old French system the Brits are still using to the metric standard of science.
foot, inch (inc 00'00"), yard, mile, stone, Pound-mass/Lbs. etc
It will totally convert something heretical like: 5'10 3/4"
The screen shots show how good and effective the script is:
I still have to implement: gallon, pints, ounces, Quarts, Hectares Acres, Fathoms, Fahrenheit and Kelvin.
Find the current version here:
Metric intervention for Greasemonkey