Pages must be simple in design. Simple HTML, non-commerical sites are preferred.
Pages should not use much scripts/css for cosmetic effect. Some might squeak through.
Don't use ads that are intrusive (such as ads that appear overtop of content).
Don't submit a page which serves primarily as a portal to other bloated websites.
If you submit a blog, submit a few of your articles, not your main feed.
If your page does not contain any text or uses frames, ensure a meta description tag is added.
Only the page you submit will be crawled.
The WibyBot (18.104.22.168) is occasionally rejected by some web servers.
Barring technical issues, if you are puzzled why a site wasn't indexed, reread the above guide.
Angelfire and Tripod pages are no longer grandfathered (ads are too intrusive).