The text-shadow property
The text-shadow property applies a drop shadow effect to the specified text, and is defined in the World Wide Web Consortium (W3C) CSS Text Decoration Module Level 3. If you are familiar with the syntax for the box-shadow property, you already know the syntax for text-shadow; they are almost identical.
A comma-separated list of shadows that attaches one or more drop shadows to the specified text. Each shadow is made up of a space-delimited list of the following:
horizontal offset Required. A positive value draws a shadow that is offset to the right of the text, a negative length to the left.
vertical offset Required. A positive value draws a shadow that is offset below the text, a negative one above.
blur distance Negative values are not allowed. If the blur value is zero, the shadow's edge is sharp. Otherwise, the larger the value, the more the shadow's edge is blurred.
spread distance Positive values cause the shadow shape to expand in all directions by the specified radius. Negative values cause the shadow shape to contract. (Be aware that this value may not be supported by all browsers.)