I have an Ionic 2 app and have the following two files in pages/home folder:
<ion-list-header class="list">Your List</ion-list-header>
I tried it with every html element and it didn't work. Made the change in the .ts file for the live reload and it still didn't apply.
Then refreshed the page also and it kicked in.
I will advice refreshing everything when it comes to html/css and on ticking "Disable cache" in developer tools in Google chrome as well.