HTML Guide for font-family

The font property should be used to set font-related attributes like font-style, font-variant, font-weight, font-size, line-height, and font-family. If you’re only trying to set font-weight, use the font-weight property instead.

Correct usage:

font-weight: 300; /* Correct syntax for setting font weight */

If you want to set multiple font properties at once, use the font shorthand correctly:

font: 300 16px/1.5 "Helvetica", sans-serif; /* font-weight font-size/line-height font-family */

Ensure that the font-family part is specified and valid.

The <tt> tag, used in HTML4 to apply a monospaced (fixed width) font to the text, was deprecated in HTML5. Instead, you should use CSS to apply the desired font.

Example, instead of this deprecated code:

<tt>This is deprecated</tt>

You can define a monospaced text using font-family:

<span style="font-family: monospace;">This is monospaced text</span>