**This variable does not have tremendous potential in terms of crawling websites, but I feel that it is worth mentioning. Most accelerators "graduate" their cohorts with a demo day, which is a day when the startups present their company to potential investors. If the website contains the words "demo day", which is fairly uncommon, it could be a good source of accelerator identification.
A combination of any of these variables would very close to certainly identify the current website as belonging to an accelerator.