What are these tiny blue lines that act as links?

So I am working on this site: http://www.newhomelaunch.org/
I tried to place social media icons above the header.

The code I used was:

Into header.php:

<div id="header_icons">

<ul>
<li><a href="http://www.twitter.com"><img src="http://www.newhomelaunch.org/wp-content/uploads/2012/10/Twitter-e1349302275170.png" /></a></li>
<li><a href="http://www.youtube.com"><img src="http://www.newhomelaunch.org/wp-content/uploads/2012/10/Youtube-e1349301570811.png" /></a></li>
<li><a href="http://www.newhomelaunch.org/feed/"><img src="http://www.newhomelaunch.org/wp-content/uploads/2012/10/Rss-e1349302295961.png" /></a></li>
</ul>
</div>

Into css:

#header_icons li{
display:inline;
position: relative;
top: 5;
right: 0;
left: 1000;
bottom: 5;
}

That worked okay, like it put stuff where I want it and they work, however, there are now those two little blue lines on the left. One links to youtube, and the other to twitter.

Any help would be appreciated. Is there a better way to do what I want? I don’t want to resize the header. I want to place either above the header or over it.