Your code looks like you may not have a good understanding of position:absolute, but it's hard to tell from a code snippet that you may have edited to present here. For example, there's no 'top' or 'left' properties in the <div> and you've got it set to width:100%. That's almost self-contradictory unless you only need to control the vertical position of the <div>.
As shown, you'd probably get something close to what you want by removing the 'position' property from the <img> tags. With those tags set to position:absolute, the margin settings are ineffective. position:absolute removes the element from the normal document flow, so there's nothing for the margins to be aligned against. It might even be best to remove everything in the 'style' attribute of the <div> tag. My advice would be to start with:
<img src="pics/clinic1.jpg" id="clinic1" style="width:910px;"/>
<img src="pics/clinic2.jpg" id="clinic2" style="width:910px;"/>
and see if that's closer to what you want.