do i need to include the language tag, and set to English. my site is all English but wondering if this tag is missing will it hurt or is it useless. thanks.
In some cases the users default may change the function and can throw off some or all of the site. So if your wanting to go after a large group of people with your site it's always best to be safe and add it.
It also helps with the "Google Translate" app as well as other extensions / add ons for language translation.... Additionally, for SEO it also allows spiders/bots to index and categorize your site based on the default language of the site. Cheers!~