http://www.w3.org/TR/css3-text/#tab-size

There are twenty-four spaces before this text. (no ID)

There are three tabs before this text. (no ID)

[#p01] There are three tabs before this text.

[#p02] There are three tabs before this text.

[#p03] There are three tabs before this text.

[#p04] There are three tabs before this text.

[#p05] There are three tabs before this text.

[#p06] There are three tabs before this text.

[#p07] The three tabs before this text should total 15 spaces wide.
[#p07] There are 15 spaces before this text.
span[#p07] The span before this text is 15ch wide.