Bizarre symbols on the buttons (Back button, home button)

Bizarre symbols on the buttons (Back button, home button)

Hi
I'm using jQM 2.2.0 on android using phonegapBuild. everything works great on ios bur I have an issue on Android smatphones only: 
on the buttons (Back button, home button) there's a symbols, like the social media symbols ! with dashes on the border of the buttons ! 

my code:

<div data-role="header" data-rel="back" data-add-back-btn="true" data-position="fixed" data-theme="b" data-tap-toggle="false"  > <!--data-rel="back" data-add-back-btn="true"-->
<a href="#"  data-icon="arrow-l"  title="Go back">Back</a> <!--data-icon="arrow-l"-->
<h1 style="font-size:14px; ;margin-left:0; margin-right:0" > History </h1>
<a href="#settings1" style="background-color:white"   data-rel="popup" data-theme="b" style="-webkit-border-radius:0px"><img src="images/font.png" height=15 width=15 ></a>
</div>

here is a screenshot: