<link href="//maxcdn.bootstrapcdn.com/bootstrap/3.3.0/css/bootstrap.min.css" rel="stylesheet" id="bootstrap-css">
<script src="//maxcdn.bootstrapcdn.com/bootstrap/3.3.0/js/bootstrap.min.js"></script>
<script src="//code.jquery.com/jquery-1.11.1.min.js"></script>
<div class="container col-xs-12 col-sm-offset-2 col-sm-8 col-md-offset-3 col-md-6 col-lg-offset-4 col-lg-4">
<br />
<div class="panel panel-default">
<div class="panel-heading">
<h1>Login</h1>
</div>
<div class="panel-body">
<div class="form-group">
<div class="input-group">
<span class="input-group-addon">
<i class="glyphicon glyphicon-user" style="width: auto"></i>
</span>
<input id="txtUsuario" runat="server" type="text" class="form-control" name="user" placeholder="Usuário" required="" />
</div>
</div>
<div class="form-group">
<div class="input-group">
<span class="input-group-addon">
<i class="glyphicon glyphicon-lock" style="width: auto"></i>
</span>
<input id="txtSenha" runat="server" type="password" class="form-control" name="password" placeholder="Senha" required="" />
</div>
</div>
<button id="btnLogin" runat="server" class="btn btn-default" style="width: 100%">
ENTRAR<i class="glyphicon glyphicon-log-in"></i>
</button>
</div>
</div>
</div>
