Format messes up when trying to use child theme

Hi. I just added a child theme which worked fine until I started adding modifications. I used firebug to view my changes and everything looked good. I then pasted the following code into the stylesheet, however, when I refreshed my page, the navigation bar is gone and the formatting is all messed up. Is there something else I need to do?

Here is my site: http://godsgarden.us/

/* This will make the height of the header area smaller*/
.header-desc {
margin: 25px 20px 10px 0;
min-height: 14px;
width: 468px;
}

/* This will make the font in the navigation bar bigger*/
nav {
display: block;
font-size: 16px;
margin: 10px -10px 0;
padding: 0 30px;
position: relative;
}

/* This will make the font of widget titles smaller*/
.widget-title h3 {
color: #FFFFFF;
font-size: 16px;
padding: 6px 0 5px 20px;
}