<form class="calc">
  <p class="calc-display">
  <input type="text" name="res" id="res" value="0" class="calc-display-input" onfocus="this.blur()">
  </p>
  <p class="calc-row">
  <button type="button" class="calc-button calc-button-gray" onclick="s('Just....')">mrc</button>
  <button type="button" class="calc-button calc-button-gray" onclick="s('....do..')">m-</button>
  <button type="button" class="calc-button calc-button-gray" onclick="s('......it')">m+</button>
  <button type="button" class="calc-button calc-button-red calc-button-big" onclick="a('/')">÷</button>
  </p>
  <p class="calc-row">
  <button type="button" class="calc-button" onclick="a('7')">7</button>
  <button type="button" class="calc-button" onclick="a('8')">8</button>
  <button type="button" class="calc-button" onclick="a('9')">9</button>
  <button type="button" class="calc-button calc-button-red calc-button-big" onclick="a('*')">x</button>
  </p>
  <p class="calc-row">
  <button type="button" class="calc-button" onclick="a('4')">4</button>
  <button type="button" class="calc-button" onclick="a('5')">5</button>
  <button type="button" class="calc-button" onclick="a('6')">6</button>
  <button type="button" class="calc-button calc-button-red calc-button-big" onclick="a('-')">-</button>
  </p>
  <p class="calc-row">
  <button type="button" class="calc-button" onclick="a('1')">1</button>
  <button type="button" class="calc-button" onclick="a('2')">2</button>
  <button type="button" class="calc-button" onclick="a('3')">3</button>
  <button type="button" class="calc-button calc-button-red calc-button-big" onclick="a('+')">+</button>
  </p>
  <p class="calc-row">
  <button type="button" class="calc-button" onclick="a('0')">0</button>
  <button type="button" class="calc-button" onclick="a('.')">.</button>
  <button type="button" class="calc-button" onclick="s('')">C</button>
  <button type="button" class="calc-button calc-button-yellow calc-button-big" onclick="e()">=</button>
  </p>
  </form>

  <script>
  function s(v) { document.getElementById('res').value = v }
  function a(v) { document.getElementById('res').value += v }
  function e() { try { s(eval(document.getElementById('res').value)) } catch(e) { s('Error') } }
  </script>

.calc {
  margin: 50px auto;
  padding: 15px;
  width: 177px;
  border: 1px solid #222;
  border-radius: 4px;
  background-color: #3d4543;
  background-image: -webkit-gradient(linear, left top, left bottom, color-stop(0%, #3d4543), color-stop(100%, #2f2a2f));
  background-image: -webkit-linear-gradient(top, #3d4543, #2f2a2f);
  background-image: -moz-linear-gradient(top, #3d4543, #2f2a2f);
  background-image: -ms-linear-gradient(top, #3d4543, #2f2a2f);
  background-image: -o-linear-gradient(top, #3d4543, #2f2a2f);
  background-image: linear-gradient(top, #3d4543, #2f2a2f);
  -webkit-box-shadow: inset 0 0 0 1px rgba(255, 255, 255, 0.1), 0 0 4px rgba(0, 0, 0, 0.5);
  box-shadow: inset 0 0 0 1px rgba(255, 255, 255, 0.1), 0 0 4px rgba(0, 0, 0, 0.5);
}

.calc-display {
  margin: 0 0 20px;
  padding: 3px;
  background: #222;
  border-radius: 3px;
  -webkit-box-shadow: inset 0 0 0 1px rgba(0, 0, 0, 0.1), 0 0 0 1px rgba(255, 255, 255, 0.08);
  box-shadow: inset 0 0 0 1px rgba(0, 0, 0, 0.1), 0 0 0 1px rgba(255, 255, 255, 0.08);
}

.calc-display-input {
  display: block;
  width: 100%;
  padding: 0 8px;
  font: 26px/35px UbuntuMono, monospace;
  color: #444;
  height: 35px;
  text-align: right;
  background-clip: padding-box;
  /* Don't let the background bleed outside the border */
  border: 1px solid #222;
  border-radius: 2px;
  background-color: #bccd95;
  background-image: -webkit-gradient(linear, left top, left bottom, color-stop(0%, #bccd95), color-stop(100%, #e0f5b1));
  background-image: -webkit-linear-gradient(top, #bccd95, #e0f5b1);
  background-image: -moz-linear-gradient(top, #bccd95, #e0f5b1);
  background-image: -ms-linear-gradient(top, #bccd95, #e0f5b1);
  background-image: -o-linear-gradient(top, #bccd95, #e0f5b1);
  background-image: linear-gradient(top, #bccd95, #e0f5b1);
  -webkit-box-shadow: inset 0 2px 3px rgba(0, 0, 0, 0.5), 0 0 0 1px rgba(255, 255, 255, 0.12);
  box-shadow: inset 0 2px 3px rgba(0, 0, 0, 0.5), 0 0 0 1px rgba(255, 255, 255, 0.12);
}

.calc-row {
  margin-top: 7px;
  zoom: 1;
}
.calc-row:before, .calc-row:after {
  content: "";
  display: table;
}
.calc-row:after {
  clear: both;
}

.calc-button {
  float: left;
  padding: 0;
  margin: 0 0 0 7px;
  width: 39px;
  font: 14px/23px UbuntuMono, monospace;
  color: white;
  text-align: center;
  text-shadow: 0 1px rgba(0, 0, 0, 0.4);
  text-decoration: none;
  background-clip: padding-box !important;
  /* !important because FF overrides the value on :active */
  border: 0;
  /* IE 8 fix */
  border: 1px solid rgba(0, 0, 0, 0.8);
  border-radius: 3px;
  cursor: pointer;
  background-color: #313131;
  background-image: -webkit-gradient(linear, left top, left bottom, color-stop(0%, #313131), color-stop(100%, #1c1c1c));
  background-image: -webkit-linear-gradient(top, #313131, #1c1c1c);
  background-image: -moz-linear-gradient(top, #313131, #1c1c1c);
  background-image: -ms-linear-gradient(top, #313131, #1c1c1c);
  background-image: -o-linear-gradient(top, #313131, #1c1c1c);
  background-image: linear-gradient(top, #313131, #1c1c1c);
  -webkit-box-shadow: inset 0 0 0 1px rgba(255, 255, 255, 0.08), 0 1px rgba(0, 0, 0, 0.3), 0 0 0 1px rgba(255, 255, 255, 0.08);
  box-shadow: inset 0 0 0 1px rgba(255, 255, 255, 0.08), 0 1px rgba(0, 0, 0, 0.3), 0 0 0 1px rgba(255, 255, 255, 0.08);
}
.calc-button:first-child {
  margin-left: 0;
}
.calc-button:active {
  background: #282828;
  -webkit-box-shadow: inset 0 1px 2px rgba(0, 0, 0, 0.6), 0 1px rgba(0, 0, 0, 0.1), 0 0 0 1px rgba(255, 255, 255, 0.05);
  box-shadow: inset 0 1px 2px rgba(0, 0, 0, 0.6), 0 1px rgba(0, 0, 0, 0.1), 0 0 0 1px rgba(255, 255, 255, 0.05);
}

.calc-button-gray {
  background-color: #6f6f6f;
  background-image: -webkit-gradient(linear, left top, left bottom, color-stop(0%, #6f6f6f), color-stop(100%, #515151));
  background-image: -webkit-linear-gradient(top, #6f6f6f, #515151);
  background-image: -moz-linear-gradient(top, #6f6f6f, #515151);
  background-image: -ms-linear-gradient(top, #6f6f6f, #515151);
  background-image: -o-linear-gradient(top, #6f6f6f, #515151);
  background-image: linear-gradient(top, #6f6f6f, #515151);
}
.calc-button-gray:active {
  background: #555;
}

.calc-button-red {
  background-color: #ff4561;
  background-image: -webkit-gradient(linear, left top, left bottom, color-stop(0%, #ff7286), color-stop(100%, #ff4561));
  background-image: -webkit-linear-gradient(top, #ff7286, #ff4561);
  background-image: -moz-linear-gradient(top, #ff7286, #ff4561);
  background-image: -ms-linear-gradient(top, #ff7286, #ff4561);
  background-image: -o-linear-gradient(top, #ff7286, #ff4561);
  background-image: linear-gradient(top, #ff7286, #ff4561);
}
.calc-button-red:active {
  background: #ff4561;
}

.calc-button-yellow {
  background-color: #ffa70c;
  background-image: -webkit-gradient(linear, left top, left bottom, color-stop(0%, #ffb935), color-stop(100%, #ffa70c));
  background-image: -webkit-linear-gradient(top, #ffb935, #ffa70c);
  background-image: -moz-linear-gradient(top, #ffb935, #ffa70c);
  background-image: -ms-linear-gradient(top, #ffb935, #ffa70c);
  background-image: -o-linear-gradient(top, #ffb935, #ffa70c);
  background-image: linear-gradient(top, #ffb935, #ffa70c);
}
.calc-button-yellow:active {
  background: #ffa70c;
}

.calc-button-big {
  font-size: 16px;
}