in below code input group is not aligned so how to fix this?
<div class="form-group">
<div class="input-group">
<span class="input-group-addon glyphicon glyphicon-envelope"></span>
<asp:TextBox ID="txt_email" CssClass="form-control" runat="server" placeholder="Email" required="required"></asp:TextBox>
</div>
</div>
