A quick Google Search, especially under 'Books' will make it amply clear that 'on the web' is predominantly used in the context of the World Wide Web.

Most of the instances of 'in the web' relate to the idiom '(caught) in the web (of ...),' etc., or if it's the www then a different phrasing such as 'in the web site,' 'in the web development' etc.

A quick Google Search, especially under 'Books' & 'News' will make it amply clear that 'on the web' is predominantly used in the context of the World Wide Web.

Most of the instances of 'in the web' relate to the idiom '(caught) in the web (of ...),' etc., or if it's the www then a different phrasing such as 'in the web site,' 'in the web development' etc.