CSS – em vs. px vs. percent

I found some examples for my students and often times, I found myself with confusions between em vs px vs %.
So I googled it and found a very useful site. Title of the page is called: CSS Font-Size: em vs. px vs. pt vs. percent
: http://kyleschaeffer.com/best-practices/css-font-size-em-vs-px-vs-pt-vs/

The site explains what each units means and how it changes based on different setups for personal settings.
At the end of the article his conclusion was that:

“In theory, the em unit is the new and upcoming standard for font sizes on the web, but in practice, the percent unit seems to provide a more consistent and accessible display for users. When client settings have changed, percent text scales at a reasonable rate, allowing designers to preserve readability, accessibility, and visual design.”

Just a little reminder that this article was released in Sep. 08.

After I read the article, I immediately wanted to adjust text size and see how the web page would look like. However, I encountered a small problem. I could not find the option in my browser. (I use chrome)
So I clicked “Help” in the menu bar, but the result turned out that if I wanna change font size of the bowser I need to make changes of my computer default font settings.

Then I found this article: http://mezzoblue.com/archives/2008/10/07/zoom/

“Somehow over the last year or two we’ve landed in a situation where most browsers now default to full page zoom instead of traditional text-resizing.
Opera has long used zoom instead of text scaling; as of IE7 Internet Explorer uses zoom to replace the older resizing method; Firefox 3 now defaults to zoom as well. Safari is really the only holdout at this point (and I suppose Chrome by extension, since they both run the same WebKit rendering engine) but, oh look, it’s coming soon to a future release.
Now it’s true that Firefox and Internet Explorer still offer the ability to scale text as they always have, but a user has to look for it; if there’s anything we’ve learned from that latter browser it’s that users aren’t inclined to change default choices on their computers, so I think it’s safe to assume most users will employ the newer method, if at all.
The implications on a designer are fairly dramatic; page zoom is an attempt to continue accurately rendering the page as it was designed, whereas text scaling simply reflows the text, often causing serious layout problems. With full page zoom, the responsibility for ensuring page integrity and legibility is moved out of the designer’s hands, and placed fully on the browser. With text resizing, the designer needs to be conscientious of the ways their layout will break at different text sizes, and compensate accordingly.
So, personal preference aside, I wonder whether designing around scaling text is still a skill we need to hold on to, and for how long. I’d be interested in hearing about reasons for and against, as I’m sure there will be both.”

It makes sense to zoom in and out to adjust one’s browser for desirable/viewable websites size for standardizing font units and more consistent layout of a page rather than changing font size.