Merge pull request jupyter#107 from willingc/html-error

Correct html errors

Author: Carreau

_includes/header.html

@@ -10,7 +10,7 @@
                     <span class="icon-bar"></span>
                 </button>
                 <a class="navbar-brand" href="{{site.baseurl}}/index.html">
-                    <img src="{{site.baseurl}}/assets/nav_logo.svg" style="height:45px;">
+                    <img src="{{site.baseurl}}/assets/nav_logo.svg" style="height:45px;" alt="Jupyter logo">
                 </a>
             </div>
             <!-- Collect the nav links, forms, and other content for toggling -->

index.html

@@ -105,7 +105,7 @@ <h2 style="text-align:center;">Currently in use at</h2>
                     <a href="http://developer.rackspace.com"><li class="col"><img src="assets/rackspace.svg" class="greydout" alt="Rackspace" height="60" width="200"></li></a>
                     <a href="https://www.quantopian.com/"><li class="col"><img src="assets/quantopian.svg" class="greydout" alt="Quantopian" height="60" width="118"></li></a>
                     <a href="http://www.netapp.com/us/"><li class="col"><img src="assets/netapp.svg" class="greydout" alt="NetApp" height="60" width="344"></li></a>
-                    <a href="https://software-carpentry.org/"><li class="col"><img src="assets/carpentry.svg" class="greydout" alt="Carpentry" height="60" width="131"></li></a>
+                    <a href="https://software-carpentry.org"><li class="col"><img src="assets/carpentry.svg" class="greydout" alt="Carpentry" height="60" width="131"></li></a>
                     <a href="https://www.janelia.org/"><li class="col"><img src="assets/janelia.svg" class="greydout" alt="Janelia" height="60" width="178"></li></a>
                     <a href="http://codeneuro.org/"><li class="col"><img src="assets/codeneuro.svg" class="greydout" alt="CodeNeuro" height="60" width="296"></li></a>
                     <a href=""><li class="col"><img src="assets/nsite.svg" class="greydout" alt="NSite" height="50" width="94"></li></a>
@@ -206,7 +206,7 @@ <h3>Interactive Computing Protocol</h3>
                     <div class="arcfeature" id="kernel">
                         <div class="container">
                             <div class="front3">
-                                <img src="assets/kernel.svg">
+                                <img src="assets/kernel.svg" alt="icon that looks like a terminal represents kernel">
                                 <a class="arc-button bt2">Learn more</a>
                             </div>
                             <div class="front3 flipped content-back">