Hi folks, Boris Zbarsky and I ran across a "not reflecting reality" issue in the WHATWG HTML spec.
The spec currently defines the rendering of the <br> element as follows: # br { content: '\A'; white-space: pre; } Source: http://www.whatwg.org/specs/web-apps/current-work/multipage/rendering.html#phrasing-content-1 This CSS implies that <br>'s rendering could be customized by CSS, which in practice (in the browsers that I tested[1]) is not actually the case. In particular: given the spec's CSS quoted above, you might expect that perhaps an author could set... "white-space: nowrap" ... on a <br> element, to neuter the linebreak. That doesn't work, though -- the <br> still triggers a linebreak. Similarly, you might also expect to be able to customize the 'display' or 'height'/'width' or 'background' properties, but in practice, none of those have any effect on <br> in modern browsers. So: to reflect reality, it might be better to specify <br> in a way that doesn't suggest it's as customizable with CSS. (for the "white-space" property in particular, but probably others as well) For reference, here's a page with a few testcases: http://people.mozilla.org/~dholbert/tests/br-tests.html The browsers that I tested[1] all agree on the rendering (basically, not honoring any of the <br> styling), with one minor exception[2]. Thanks, ~Daniel [1] I tested the following browsers: Firefox 26 Opera 12.16 Chrome 34.0.1788.0 dev IE 11 [2] I only noticed one rendering difference -- IE11 honors "border" on <br>, unlike the other browsers that I tested. (It still doesn't honor e.g. "display"/"width"/"height", though.)