Your definition for 'mod' doesn't seem right.
As far as I know a stock is a stock because the bike was used more or less how it came.
For mods, the original ones were heavily modified bmx bikes. You can see early pictures where they put triple clamp forks on, put the handlebars much further forwards, stuck a much lighter gear on there and welded rails to the bottom of the frame to protect the sprocket. You could use a stock as a mountain bike still but a mod is quite a lot different from an old bmx.
Also on that same page, you've got some Random odd capiTal letters sneaking in there where they'Re not needed. Actually, they're all over your website. You use a capital letter for a proper noun. A tailwhip, for example, unless, God forbid, it's someone's name or the name of a place, doesn't need to be capital. Lots of kids these days make the mistake of thinking 'this is an important word, it needs a capital letter.'