CSS Outline

Outlines are special visual properties similar to border, but take up no space in the layout. They will highlight an item without shifting its position.
An outline is a line that is drawn around elements, outside the border edge, to make the element "stand out". It specifies the style, color, and width of an outline, but don't have separate definitions for each of the four sides.

outline-color

The outline-color property sets the color of an outline.
- Values:

invert - Makes a color inversion. This ensures that the outline is visible, regardless of color background (default).
name - specify a color name (blue, green, ...).
RGB - specify a RGB value, like "rgb(10,20,250)".
Hex - A hex value (#0101ff , #a8feb8).

- Syntax:

outline-color: value;

The "outline-color" does not work if it is used alone. You need to define the "outline-style" property before the "outline-color".

outline-style

The outline-style property specifies what kind of line to display. You can define one of the fallowing values:

none, solid, dashed, dotted, double, groove, ridge, inset, outset

- none specifies no outline. In the image below you can see the effect of the other values:
css outline-style

- Syntax:

outline-style: value;

outline-width

The outline-width sets the size of the border.
- Values:

length - A pixel (px) value that defines the thickness of the outline.
thin - A thin outline.
medium - A medium outline (default).
thick - Specifies a thick outline.

- Syntax:

outline-width: value;

Example:

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html>
<head>
 <title>outline</title>
 <style type="text/css"><!--
 #idd {
  outline-style: dashed;
  outline-width: 2px;
  outline-color: blue;
 }
 --></style>
</head>
<body>
 <div id="idd">Free Web Development courses and resources.</div>
</body>
</html>

- Result:

Free Web Development courses and resources

outline shorthand

Using the outline shorthand property you can shorten the code. It accept three values representing outline-width, outline-style, and outline-color.
- Syntax:

selector { outline: width_val style_val color_val; }

The CSS code from the above example can be rewritten like this (the effect is the same):

#idd { outline: 2px dashed blue; }

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