Iteration of Ionic Icons

Hi there Fellas,
I need to insert some icons on my web app. i have inserted all the required commands and my code shows no errors, but the icons won’t show in the navigation bar.

Code I used:

<!--Basic: auto-select the icon based on the platform -->
  <ion-icon name="arrow-back"></ion-icon>

  <!-- Advanced: explicity set the icon for each platform -->
  <ion-icon ios="ios-arrow-back" md="md-arrow-back"></ion-icon>

See Icons on my website.