Bootstrap/scss/_scaffolding.scss

//
// Scaffolding
// --------------------------------------------------


// Reset the box-sizing
//
// Heads up! This reset may cause conflicts with some third-party widgets.
// For recommendations on resolving such conflicts, see
// http://getbootstrap.com/getting-started/#third-box-sizing
// Credit: Jon Neal & CSS-Tricks
// http://css-tricks.com/inheriting-box-sizing-probably-slightly-better-best-practice/
html {
  box-sizing: border-box;
}
*,
*:before,
*:after {
  box-sizing: inherit;
}


// Make viewport responsive
//
// @viewport is supposed to eventually replace <meta name="viewport">. It's manually prefixed for forward-compatibility.
//
// @viewport is also needed because IE 10+ doesn't honor <meta name="viewport"> in some cases.
// (See http://timkadlec.com/2012/10/ie10-snap-mode-and-responsive-design/)
//
// However, `device-width` is broken on IE 10 on Windows (Phone) 8,
// (see http://timkadlec.com/2013/01/windows-phone-8-and-device-width/
// and https://github.com/twbs/bootstrap/issues/10497)
// and the fix for that involves a snippet of JavaScript to sniff the user agent and apply some conditional CSS.
// See http://getbootstrap.com/getting-started/#support-ie10-width for the relevant hack.

@-moz-viewport      { width: device-width; }
@-ms-viewport       { width: device-width; }
@-o-viewport        { width: device-width; }
@-webkit-viewport   { width: device-width; }
@viewport           { width: device-width; }


// Body reset

html {
  font-size: $font-size-root;
  -webkit-tap-highlight-color: rgba(0,0,0,0);
}

body {
  font-family: $font-family-base;
  font-size: $font-size-base;
  line-height: $line-height-base;
  color: $text-color;
  background-color: $body-bg;
}

// Reset fonts for relevant elements
input,
button,
select,
textarea {
  font-family: inherit;
  font-size: inherit;
  line-height: inherit;
}


// Links

a {
  color: $link-color;
  text-decoration: none;

  @include hover-focus {
    color: $link-hover-color;
    text-decoration: $link-hover-decoration;
  }

  &:focus {
    @include tab-focus();
  }
}


// Images

img {
  vertical-align: middle;
}

// Responsive images (ensure images don't scale beyond their parents)
.img-responsive {
  @include img-responsive();
}

// Rounded corners
.img-rounded {
  @include border-radius($border-radius-lg);
}

// Image thumbnails
.img-thumbnail {
  padding: $thumbnail-padding;
  line-height: $line-height-base;
  background-color: $thumbnail-bg;
  border: 1px solid $thumbnail-border;
  border-radius: $thumbnail-border-radius;
  transition: all .2s ease-in-out;
  @include box-shadow(0 1px 2px rgba(0,0,0,.075));

  // Keep them at most 100% wide
  @include img-responsive(inline-block);
}

// Perfect circle
.img-circle {
  border-radius: 50%; // set radius in percents
}


// Horizontal rules

hr {
  margin-top: $spacer;
  margin-bottom: $spacer;
  border: 0;
  border-top: .0625rem solid $hr-border;
}


// Only display content to screen readers
//
// See: http://a11yproject.com/posts/how-to-hide-content/

.sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0,0,0,0);
  border: 0;
}

// Use in conjunction with .sr-only to only display content when it's focused.
// Useful for "Skip to main content" links; see http://www.w3.org/TR/2013/NOTE-WCAG20-TECHS-20130905/G1
// Credit: HTML5 Boilerplate

.sr-only-focusable {
  &:active,
  &:focus {
    position: static;
    width: auto;
    height: auto;
    margin: 0;
    overflow: visible;
    clip: auto;
  }
}