I've spent a lot of time finding apps I trust enough to leave my kids mostly unsupervised with. For me it's mostly boiled down to finding trustworthy app publishers, I listed some here a while ago: https://medium.com/@jacksonpauls/apps-for-preschool-kids-304...
One thing I've noticed is that bing webmaster tools will report "The title is missing in the head section of the page" when there is a title, but no <head>. Maybe bing can't properly crawl pages without a <head>. Another service I've used had the same problem, but can't remember which.
So it might be worth being careful with omitting <head> - and maybe other tags, I'm reconsidering whether it's a good idea.
"In addition, the Government will work with organizations such as the Linux Foundation’s Core Infrastructure Initiative to fund and secure commonly used internet “utilities” such as open-source software, protocols, and standards. Just as our roads and bridges need regular repair and upkeep, so do the technical linkages that allow the information superhighway to flow."