zoom+html+css,html - how to set zoom level using css - Stack Overflow

What DA said, zoom is a user controlled setting, but you can size things relative to the zoom, and if users don't use Ctr + - to size, but change the sizing by setting a default font size, you can can over-ride this default setting by setting a font-size in pixels (as opposed to ems, %, etc.).... This however, is generally considered bad practice, since it may make the lettering / sizing illegible and unchangeable to some people, who don't know about Ctr + - and rely on a default font size.

You can adjust sizing relative to the user defaults and zoom setting by setting the font-size in ems or %. This will change the sizing of things relative to the user set sizing.

This enables you to make each page look to another person how it looks to you.... since each person's perception of "small," "medium," and "large" is different.