vendorSub is the substring of the vendor having to do with the vendor version number.
venSub = window.navigator.vendorSub
venSubis a string.
window.navigator.vendorSub // returns "6.1" where the vendor part of userAgent is // Netscape6/6.1
vendorSub is yet another component of the full user agent string. It refers to the version number that the vendor themselves have given the current browser (as opposed to the version of the product, which may be different). In Netscape 6.1, the productSub is given as "5.0" and the vendorSub is "6.1." See also
DOM Level 0. Not part of any standard.