Font Size
The font-size property sets the size of the text.
Being able to manage the text size is important in web design. However, you should not use font size adjustments to make paragraphs look like headings, or headings look like paragraphs.
Always use the proper HTML tags, like <h1> - <h6> for headings and <p> for paragraphs.
The font-size value can be an absolute, or relative size.
Absolute size:
- Sets the text to a specified size
- Does not allow a user to change the text size in all browsers (bad for accessibility reasons)
- Absolute size is useful when the physical size of the output is known
Relative size:
- Sets the size relative to surrounding elements
- Allows a user to change the text size in browsers
* If you do not specify a font size, the default size for normal text, like paragraphs, is 16px (16px=1em).
Set Font Size With Pixels
Setting the text size with pixels gives you full control over the text size:
Example
h1 {font-size:40px;}
h2 {font-size:30px;}
p {font-size:14px;}
h2 {font-size:30px;}
p {font-size:14px;}
The example above allows Internet Explorer 9, Firefox, Chrome, Opera, and Safari to resize the text.
Note: The example above does not work in IE, prior version 9.
The text can be resized in all browsers using the zoom tool (however, this resizes the entire page, not just the text).
Set Font Size With Em
To avoid the resizing problem with older versions of Internet Explorer, many developers use em instead of pixels.
The em size unit is recommended by the W3C.
1em is equal to the current font size. The default text size in browsers is 16px. So, the default size of 1em is 16px.
The size can be calculated from pixels to em using this formula: pixels/16=em
Example
h1 {font-size:2.5em;} /* 40px/16=2.5em */
h2 {font-size:1.875em;} /* 30px/16=1.875em */
p {font-size:0.875em;} /* 14px/16=0.875em */
h2 {font-size:1.875em;} /* 30px/16=1.875em */
p {font-size:0.875em;} /* 14px/16=0.875em */
In the example above, the text size in em is the same as the previous example in pixels. However, with the em size, it is possible to adjust the text size in all browsers.
Unfortunately, there is still a problem with older versions of IE. The text becomes larger than it should when made larger, and smaller than it should when made smaller.
Use a Combination of Percent and Em
The solution that works in all browsers, is to set a default font-size in percent for the <body> element:
Example
body {font-size:100%;}
h1 {font-size:2.5em;}
h2 {font-size:1.875em;}
p {font-size:0.875em;}
h1 {font-size:2.5em;}
h2 {font-size:1.875em;}
p {font-size:0.875em;}
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