CSS Selector Examples: Classes, Combinations and Media Queries

/* Basic CSS with class selectors */
.container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 20px;
}

.header {
  background-color: #333;
  color: white;
  padding: 15px;
}

.nav-bar {
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.button {
  padding: 10px 20px;
  border: none;
  border-radius: 5px;
  cursor: pointer;
}

.button-primary {
  background-color: #007bff;
  color: white;
}

.button-secondary {
  background-color: #6c757d;
  color: white;
}

.card {
  border: 1px solid #ddd;
  border-radius: 8px;
  padding: 20px;
  margin-bottom: 20px;
}

.card-title {
  font-size: 24px;
  font-weight: bold;
  margin-bottom: 10px;
}

.card-body {
  color: #666;
  line-height: 1.6;
}

.row {
  display: flex;
  flex-wrap: wrap;
  margin: -10px;
}

.col {
  flex: 1;
  padding: 10px;
}

.text-center {
  text-align: center;
}

.text-right {
  text-align: right;
}

.mt-1 { margin-top: 0.5rem; }
.mt-2 { margin-top: 1rem; }
.mt-3 { margin-top: 1.5rem; }
.mb-1 { margin-bottom: 0.5rem; }
.mb-2 { margin-bottom: 1rem; }
.p-1 { padding: 0.5rem; }
.p-2 { padding: 1rem; }

/* CSS with ID selectors */
#main {
  width: 100%;
  max-width: 1200px;
  margin: 0 auto;
}

#header {
  background: #333;
  padding: 20px;
}

#logo {
  font-size: 24px;
  font-weight: bold;
  color: white;
  text-decoration: none;
}

#navigation {
  display: flex;
  list-style: none;
  margin: 0;
  padding: 0;
}

#navigation li {
  margin-right: 20px;
}

#navigation a {
  color: white;
  text-decoration: none;
}

#content {
  padding: 40px 20px;
}

#sidebar {
  width: 300px;
  float: left;
}

#main-content {
  margin-left: 320px;
}

#footer {
  background: #333;
  color: white;
  padding: 20px;
  text-align: center;
  clear: both;
}

#search-box {
  width: 300px;
  padding: 10px;
  border: 1px solid #ddd;
  border-radius: 5px;
}

#submit-button {
  background: #007bff;
  color: white;
  padding: 10px 20px;
  border: none;
  border-radius: 5px;
  cursor: pointer;
}

#hero-section {
  background-image: url('hero.jpg');
  background-size: cover;
  height: 500px;
  display: flex;
  align-items: center;
  justify-content: center;
}

#hero-title {
  font-size: 48px;
  color: white;
  text-shadow: 2px 2px 4px rgba(0,0,0,0.5);
}

#contact-form {
  max-width: 500px;
  margin: 0 auto;
}

#map-container {
  width: 100%;
  height: 400px;
  background: #f0f0f0;
}

/* Combined selectors - classes, IDs, elements, and pseudo-classes */
.container #header {
  background: #333;
  padding: 20px;
}

.nav-bar .menu-item {
  display: inline-block;
  margin-right: 20px;
}

.nav-bar .menu-item:hover {
  color: #007bff;
}

.nav-bar .menu-item.active {
  font-weight: bold;
  color: #007bff;
}

.button-primary:hover {
  background-color: #0056b3;
}

.button-primary:active {
  transform: translateY(2px);
}

.card .card-title {
  font-size: 24px;
  font-weight: bold;
}

.card .card-body p {
  line-height: 1.6;
  color: #666;
}

.form-group input[type="text"] {
  width: 100%;
  padding: 10px;
  border: 1px solid #ddd;
}

.form-group input[type="email"] {
  width: 100%;
  padding: 10px;
  border: 1px solid #ddd;
}

.form-group textarea {
  width: 100%;
  padding: 10px;
  border: 1px solid #ddd;
  min-height: 100px;
}

.dropdown-menu {
  display: none;
  position: absolute;
  background: white;
  border: 1px solid #ddd;
  min-width: 200px;
}

.dropdown:hover .dropdown-menu {
  display: block;
}

.table-striped tr:nth-child(odd) {
  background-color: #f9f9f9;
}

.table-striped tr:nth-child(even) {
  background-color: #fff;
}

.alert-success {
  background-color: #d4edda;
  color: #155724;
  padding: 15px;
  border-radius: 5px;
}

.alert-error {
  background-color: #f8d7da;
  color: #721c24;
  padding: 15px;
  border-radius: 5px;
}

.pagination .page-item:first-child .page-link {
  border-top-left-radius: 5px;
  border-bottom-left-radius: 5px;
}

.pagination .page-item:last-child .page-link {
  border-top-right-radius: 5px;
  border-bottom-right-radius: 5px;
}

.input-group .input-group-addon {
  background-color: #e9ecef;
  border: 1px solid #ced4da;
  padding: 10px;
}

.modal .modal-header {
  padding: 15px;
  border-bottom: 1px solid #dee2e6;
}

.modal .modal-body {
  padding: 15px;
}

.modal .modal-footer {
  padding: 15px;
  border-top: 1px solid #dee2e6;
}

/* CSS with media queries */
.container {
  width: 100%;
  max-width: 1200px;
  margin: 0 auto;
  padding: 20px;
}

@media (max-width: 1200px) {
  .container {
    max-width: 960px;
  }

  .col-md-6 {
    width: 50%;
    float: left;
  }
}

@media (max-width: 992px) {
  .container {
    max-width: 720px;
  }

  .col-sm-12 {
    width: 100%;
  }

  .header {
    padding: 10px;
  }
}

@media (max-width: 768px) {
  .container {
    max-width: 540px;
    padding: 15px;
  }

  .nav-bar {
    flex-direction: column;
    align-items: flex-start;
  }

  .nav-bar .menu-item {
    margin-right: 0;
    margin-bottom: 10px;
  }

  .sidebar {
    width: 100%;
    float: none;
  }

  .main-content {
    margin-left: 0;
  }
}

@media (max-width: 576px) {
  .container {
    max-width: 100%;
    padding: 10px;
  }

  .button {
    width: 100%;
    margin-bottom: 10px;
  }

  .card {
    padding: 15px;
  }

  .card-title {
    font-size: 20px;
  }
}

@media print {
  .container {
    max-width: 100%;
  }

  .no-print {
    display: none;
  }

  .print-only {
    display: block;
  }

  a[href]:after {
    content: " (" attr(href) ")";
  }
}

@media (min-width: 992px) and (max-width: 1200px) {
  .col-lg-4 {
    width: 33.333%;
    float: left;
  }
}

@media (orientation: landscape) {
  .banner {
    height: 300px;
  }
}

@media (orientation: portrait) {
  .banner {
    height: 200px;
  }
}

/* CSS with keyframes and animations */
@keyframes fadeIn {
  from {
    opacity: 0;
  }
  to {
    opacity: 1;
  }
}

@keyframes slideIn {
  0% {
    transform: translateX(-100%);
  }
  100% {
    transform: translateX(0);
  }
}

@keyframes bounce {
  0%, 20%, 50%, 80%, 100% {
    transform: translateY(0);
  }
  40% {
    transform: translateY(-20px);
  }
  60% {
    transform: translateY(-10px);
  }
}

@keyframes rotate {
  from {
    transform: rotate(0deg);
  }
  to {
    transform: rotate(360deg);
  }
}

@keyframes pulse {
  0% {
    transform: scale(1);
  }
  50% {
    transform: scale(1.1);
  }
  100% {
    transform: scale(1);
  }
}

@keyframes shake {
  0%, 100% {
    transform: translateX(0);
  }
  10%, 30%, 50%, 70%, 90% {
    transform: translateX(-10px);
  }
  20%, 40%, 60%, 80% {
    transform: translateX(10px);
  }
}

.animate-fadeIn {
  animation: fadeIn 1s ease-in;
}

.animate-slideIn {
  animation: slideIn 0.5s ease-out;
}

.animate-bounce {
  animation: bounce 1s infinite;
}

.animate-rotate {
  animation: rotate 2s linear infinite;
}

.animate-pulse {
  animation: pulse 2s ease-in-out infinite;
}

.animate-shake:hover {
  animation: shake 0.5s;
}

@-webkit-keyframes slideUp {
  from {
    -webkit-transform: translateY(100%);
  }
  to {
    -webkit-transform: translateY(0);
  }
}

@-moz-keyframes flash {
  0%, 50%, 100% {
    opacity: 1;
  }
  25%, 75% {
    opacity: 0;
  }
}

/* SCSS-like nested selectors */
.container {
  width: 100%;
  max-width: 1200px;
  margin: 0 auto;
  padding: 20px;
}

.container .header {
  background: #333;
  padding: 20px;
}

.container .header .logo {
  font-size: 24px;
  color: white;
}

.container .header .nav {
  display: flex;
  justify-content: space-between;
}

.container .header .nav .menu-item {
  margin-right: 20px;
}

.container .header .nav .menu-item:hover {
  color: #007bff;
}

.container .content {
  padding: 40px 20px;
}

.container .content .sidebar {
  width: 300px;
  float: left;
}

.container .content .sidebar .widget {
  background: #f5f5f5;
  padding: 20px;
  margin-bottom: 20px;
}

.container .content .sidebar .widget .widget-title {
  font-size: 18px;
  font-weight: bold;
  margin-bottom: 10px;
}

.container .content .main {
  margin-left: 320px;
}

.container .content .main .article {
  margin-bottom: 30px;
}

.container .content .main .article .article-title {
  font-size: 32px;
  margin-bottom: 15px;
}

.container .content .main .article .article-meta {
  color: #999;
  font-size: 14px;
  margin-bottom: 15px;
}

.container .content .main .article .article-content {
  line-height: 1.8;
  color: #333;
}

.container .content .main .article .article-content p {
  margin-bottom: 15px;
}

.container .footer {
  background: #333;
  color: white;
  padding: 20px;
  text-align: center;
}

.dropdown {
  position: relative;
}

.dropdown .dropdown-toggle {
  background: #007bff;
  color: white;
  padding: 10px 20px;
  border: none;
  cursor: pointer;
}

.dropdown .dropdown-menu {
  display: none;
  position: absolute;
  top: 100%;
  left: 0;
  background: white;
  border: 1px solid #ddd;
  min-width: 200px;
  z-index: 1000;
}

.dropdown:hover .dropdown-menu {
  display: block;
}

.dropdown .dropdown-menu .dropdown-item {
  padding: 10px 20px;
  display: block;
  color: #333;
  text-decoration: none;
}

.dropdown .dropdown-menu .dropdown-item:hover {
  background: #f5f5f5;
}

/* CSS with pseudo-classes and pseudo-elements */
a:hover {
  color: #007bff;
  text-decoration: underline;
}

a:visited {
  color: #6c757d;
}

a:active {
  color: #0056b3;
}

a:focus {
  outline: 2px solid #007bff;
  outline-offset: 2px;
}

input:focus {
  border-color: #007bff;
  box-shadow: 0 0 0 0.2rem rgba(0, 123, 255, 0.25);
}

button:disabled {
  opacity: 0.6;
  cursor: not-allowed;
}

input:checked + label {
  font-weight: bold;
}

input:required {
  border-color: #dc3545;
}

input:valid {
  border-color: #28a745;
}

input:invalid {
  border-color: #dc3545;
}

:first-child {
  font-weight: bold;
}

:last-child {
  margin-bottom: 0;
}

:nth-child(odd) {
  background-color: #f9f9f9;
}

:nth-child(even) {
  background-color: #fff;
}

:nth-child(3n) {
  border-left: 2px solid #007bff;
}

:first-of-type {
  text-transform: uppercase;
}

:last-of-type {
  margin-right: 0;
}

:not(.exclude) {
  padding: 10px;
}

:lang(en) {
  font-family: Arial, sans-serif;
}

::before {
  content: "\2192";
  margin-right: 5px;
}

::after {
  content: "\2190";
  margin-left: 5px;
}

::first-letter {
  font-size: 24px;
  font-weight: bold;
  color: #007bff;
}

::first-line {
  font-weight: bold;
  color: #333;
}

::selection {
  background: #007bff;
  color: white;
}

::placeholder {
  color: #999;
  font-style: italic;
}

li:first-child::before {
  content: "First: ";
}

li:last-child::after {
  content: " (Last)";
}

p:not(.exclude)::first-line {
  font-weight: bold;
}

a.external::after {
  content: "\2197";
}

/* CSS with attribute selectors */
input[type="text"] {
  width: 100%;
  padding: 10px;
  border: 1px solid #ddd;
}

input[type="email"] {
  width: 100%;
  padding: 10px;
  border: 1px solid #ddd;
}

input[type="password"] {
  width: 100%;
  padding: 10px;
  border: 1px solid #ddd;
}

input[type="submit"] {
  background: #007bff;
  color: white;
  padding: 10px 20px;
  border: none;
  border-radius: 5px;
  cursor: pointer;
}

a[href^="https://"] {
  color: #28a745;
}

a[href^="http://"] {
  color: #dc3545;
}

a[href^="#"] {
  color: #007bff;
}

a[href$=".pdf"]::after {
  content: " (PDF)";
}

a[href$=".doc"]::after {
  content: " (DOC)";
}

a[href$=".xls"]::after {
  content: " (XLS)";
}

img[alt] {
  border: 2px solid #28a745;
}

img[alt=""] {
  border: 2px solid #dc3545;
}

[class*="col-"] {
  float: left;
  padding: 10px;
}

[data-toggle="dropdown"] {
  cursor: pointer;
}

[data-dismiss="modal"] {
  background: #dc3545;
  color: white;
  border: none;
  padding: 5px 10px;
  cursor: pointer;
}

[data-target^="#collapse"] {
  cursor: pointer;
}

[data-spy="scroll"] {
  position: relative;
}

[aria-hidden="true"] {
  display: none;
}

[aria-expanded="true"] .icon {
  transform: rotate(180deg);
}

[disabled] {
  opacity: 0.6;
  cursor: not-allowed;
}

[readonly] {
  background-color: #f5f5f5;
  cursor: not-allowed;
}

[required] {
  border-color: #dc3545;
}

[multiple] {
  height: 100px;
}

[name="email"] {
  width: 100%;
}

[name~="first-name"] {
  width: 48%;
}

[name|="en"] {
  font-family: Arial, sans-serif;
}

input[class~="form-control"] {
  border: 1px solid #ced4da;
}

a[rel~="nofollow"] {
  color: #999;
}

div[id^="section-"] {
  padding: 20px;
  margin-bottom: 20px;
}

div[id$="-container"] {
  background: #f5f5f5;
  padding: 20px;
}

[data-info*="user"] {
  font-weight: bold;
}