CSS
Instead of having 5 different rules all saying the same thing for 5 selectors. You can group them like this.
h1.light,
h2.light,
.darkgrey a,
.darkestgrey a,
.button.light
{
color: #fff;
}
body,
.underline.light {
background-color: #fff;
}
Use one line for margins.
h1 {
margin-top: 20px 0;
}
h2 {
margin: 0 0 20px 0;
}
.underline {
margin: 20px auto 30px;
}
.button {
margin: 20px auto 20px -160px;
}
.nextbutton {
margin: 20px 0;
}
Use one line for paddings.
.container {
padding: 30px 0;
}
.column.third {
padding: 30px 0;
}
HTML
You should remove this from your head.
<meta name="keywords" content="3D, interactive, virtual, simulations, training, games, gamification">
Most search engines do not use the meta keywords for their algorithm top rankings anymore. From what I've heard, having the meta keywords can only count against you for SEO (Search Engine Optimization). Because I believe that search engines will still penalize a site for having false and or repetitive keywords. Yes, your keywords are correct, but there is no point in including them on websites anymore. http://en.wikipedia.org/wiki/Meta_element#The_keywords_attribute