Add stroke around text – on the outside – with css?

For a smooth outside stroke emulated by text shadow, use the following 8-axis shadow:

  text-shadow:
    -1px -1px 0 #000,
     0   -1px 0 #000,
     1px -1px 0 #000,
     1px  0   0 #000,
     1px  1px 0 #000,
     0    1px 0 #000,
    -1px  1px 0 #000,
    -1px  0   0 #000;

For customisation, you can use this SASS mixin instead (although changing the size does have side effects on rendering):

@mixin stroke($color: #000, $size: 1px) {
  text-shadow:
    -#{$size} -#{$size} 0 $color,
     0        -#{$size} 0 $color,
     #{$size} -#{$size} 0 $color,
     #{$size}  0        0 $color,
     #{$size}  #{$size} 0 $color,
     0         #{$size} 0 $color,
    -#{$size}  #{$size} 0 $color,
    -#{$size}  0        0 $color;
}

This gives a very smooth stroke, without missing parts, like on the 4 axis solution.