W003 - Herst/bootlint-ng GitHub Wiki
Note: Below is the original page from the Bootlint documentation, some of the info here might not apply to Bootlint-NG!
To enable responsive viewport sizing in most modern mobile browsers, the webpage needs to include an appropriate <meta name="viewport"> tag in its <head>, such as:
<meta name="viewport" content="width=device-width, initial-scale=1">Bootlint didn't find such a <meta name="viewport"> tag in the webpage. Unless you're using Bootstrap in a non-responsive fashion, you should add the tag.
See also: Bootstrap's basic HTML template