为表单加上bootstrap 风格的focus CSS ( adding bootstrap style focus CSS to your input field)

add these line to your CSS file: 

textarea:focus, input[type="text"]:focus, input[type="password"]:focus, input[type="datetime"]:focus, inpu
t[type="datetime-local"]:focus, input[type="date"]:focus, input[type="month"]:focus, input[type="time"]:focus, input[type="week"]:focus, input[type="number"]:focus, input[type="email"]:focus, input[type="url"]:focus, input[type="search"]:focus, input[type="tel"]:focus, input[type="color"]:focus, .uneditable-input:focus {
  border: 1px solid #7F9EF4;
  -webkit-box-shadow: inset 0 1px 1px rgba(0, 0, 0, 0.075), 0 0 6px #7ab5d3;
  -moz-box-shadow: inset 0 1px 1px rgba(0, 0, 0, 0.075), 0 0 6px #7ab5d3;
  box-shadow: inset 0 1px 1px rgba(0, 0, 0, 0.075), 0 0 6px #7ab5d3;
}