Make sure that the content is readable, even if the user doubles the size of the text in the browser. Therefore you need to prevent the overlapping of text, text disappearing off the screen, etc.
To ensure that this recommendation is respected as far as possible, you are advised:
Not to use units (
px,
pt,
%,
em, etc.) with the property
CSS line-height.
Not to define a fixed height for elements that are likely to have text content, especially form fields.
Not to define the width of elements in em.
Tip
To test this criteria:
With Firefox, select the menu View, select Zoom and then select Zoom text only, and then double the size of the text by clicking 6 times with the keyboard shortcut CTRL and + (CTRL and 0 returns the size to the default size).
With Internet Explorer, in the View menu, select Text size, then select Largest.