HTML Linked Images Issues

When working on an HTML email signature, I wrote basic HTML for four linked images.

<a href="http://ift.tt/1E9jnHB">
<img src="http://ift.tt/1zHI3vn" width="40" height="40" alt="capture"/>
</a>
<a href="http://ift.tt/1E9jnHF">
<img src="http://ift.tt/1zHI3vp" width="40" height="40" alt="capture" border="0">
</a>
<a href="http://ift.tt/1E9jqD5">
<img src="http://ift.tt/1zHI3vu" width="40" height="40" alt="capture"/>
</a>
<a href="http://ift.tt/1E9jqDc">
<img src="http://ift.tt/1zHI4PY" width="40" height="40" alt="capture"/>
</a>

When I view the code in my browser these weird lines appear next to the images like below:

Why are these lines there any how can I remove them?