text-shadow: h-shadow v-shadow blur-radius color
If the shadow isn't intense enough, you can repeat it multiple times.
The following example use a white text with black outline (intensity is repeated 4 times).
color: #fff;/* thick outline */text-shadow: -1px -1px 1px #000, 1px -1px 1px #000, -1px 1px 1px #000, 1px 1px 1px #000;/* thin outline */text-shadow: 0px 0px 1px #000, 0px 0px 1px #000, 0px 0px 1px #000, 0px 0px 1px #000;/* thick 3D-effect */text-shadow: 1px 1px 1px #000, 1px 1px 1px #000, 1px 1px 1px #000, 1px 1px 1px #000;/* thin 3D-effect */text-shadow: 1px 1px 0px #000, 1px 1px 0px #000, 1px 1px 0px #000, 1px 1px 0px #000;