Making every character on a web page the same width

CSS:

font-family: monospace;

HTML:

<tt>

If you only need numbers to be equal widths, you can use font-variant-numeric: tabular-nums;. It's really useful for animating counters. Read more about it on Mozilla web docs.

How about Courier New? monospace?

http://www.ampsoft.net/webdesign-l/WindowsMacFonts.html