The horizontal tab character
The horizontal tab character (decimal 9 in [link|http://www.w3.org/TR/html4/references.html#ref-ISO10646|[ISO10646]] and [link|http://www.w3.org/TR/html4/references.html#ref-ISO88591|[ISO88591]] ) is usually interpreted by visual user agents as the smallest non-zero number of spaces necessary to line characters up along tab stops that are every 8 characters. We strongly discourage using horizontal tabs in preformatted text since it is common practice, when editing, to set the tab-spacing to other values, leading to misaligned documents.
See it [link|http://www.w3.org/TR/html4/struct/text.html#h-9.3.4|here].
Eight shalt be the number thou shalt count, and the number of the counting shall be eight. :-)