Typography generally refers to font faces, font sizing, and the alignment and spacing of type. As a designer and developer, it's important to consider the readability of text and the visual cues that typographical techniques offer the reader. Typography on the Web involves more than just the six levels of heading elements and default text. With CSS, you have better control over the appearance of your text.
The ability to control typography on the Web is relatively new. HTML was never intended to handle typographical styles, and the font tag and its face, color and size attributes are not only severely limited in their power and flexibility, they're a bad idea altogether. The font tag and its attributes are deprecated in HTML 4.0 in favor of style sheets, although it has taken quite a while for browsers to mature to the point where it's safe to use CSS to control your typography.
Font face and size are the two most fundamental aspects of type. With CSS, you can control the size of your type with the font-size property and specify the font faces you want using the font-family property.
Consider the following guidelines:
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