Question

I still use EM’s in the CSS to specify the sizes of elements in my templates.

Today most browsers are able to correctly scale websites where the sizes are given in PX.

My argument for using EM’s was / is: if a person that has a sight disability and changes the base font size in the browser, the design still fits.

I’m asking because for me its still a source of errors to use EM’s. When i specify a different font-size then the base font-size on a element, I often forget to adapt my EM calculation for the children elements.

Now i have 2 questions:

1. How do people with a sight
   disability configure the browser (do
   they use the browser zoom or do they
   still change the base font-size)?

2. Does it still make sense to use EM’s
   for element sizes nowadays?

Answer 1

1. Based on what I’ve read, neither. Users with mild-to-moderate sight difficulties often use applications distinct from the UA itself to provide zooming functions. These tools can magnify all or part of a display, but (in my limited experience) they don’t zoom the text out-of-relation to the setting.

2. It still makes sense to use ’em’. First of all, accessibility isn’t the only reason to use ’ems’. I think the inheritance model of relative sizes makes more sense with ems and percentages than it does with pixels. Second, you can do calculations in CSS3 itself, if it helps you to not need to remember to adapt your calculations.

refs:

• http://www.championinternet.com/rwa/Ann.pdf
• http://davidbcalhoun.com/2010/does-it-still-make-sense-to-use-em-rather-than-px
• http://www.w3.org/TR/css3-values/#calc