I'm trying to think responsive, in terms of web design. First silly test I do: open a blank file, put it some text inside. Big amount of text (lorem ipsum, whatever). Even without any HTML markup. Save the file with .html extension, and open it with any modern browser: Chrome, Firefox, IE, Safari...
If you change the size of the window (the viewport size) the text automatically wraps to fit in the screen. No DOCTYPE declaration, no meta tags. Nothing. Just plain text.
Why do the browser automatically wrap text to fit in the screen? Do they have any default responsive behaviour? Under what criteria?