Header in Mobile device / Bootstrap

I have a project using bootstrap . Since in the documentation you don't have to build mobile version ( unchecked ) Is there a way to change the header size and footer size in the welcome page or anyother page for that matter when a mobile device connects? Using three images. my code for the desktop version below
<P></P>

<P align="center"><IMG width="200" height="70" align="textTop" style="width: 165px; height: 62px;"

src="https://asprunner.com/forums/file.php?topicimage=1&fieldname=question&id=24267&image=1&table=forumtopics"; border="0"> <IMG

width="200" height="70" align="textTop" style="width: 750px; height: 91px;" src="https://asprunner.com/forums/file.php?topicimage=1&fieldname=question&id=24267&image=2&table=forumtopics";

border="0"><IMG width="200" height="70" align="textTop" style="width: 165px; height: 62px;"

src="https://asprunner.com/forums/file.php?topicimage=1&fieldname=question&id=24267&image=3&table=forumtopics";

border="0"></P>