CSS issues

Freestyle has five CSS errors when validated as CSS 2.1 at http://d-theme.com/freestyle and one error when validated as CSS 3:
URI : http://d-theme.com/sites/all/themes/freestyle/style.css?s
353 #footer p Property -x-system-font doesn't exist : none

With or without that error, the theme is not easy to make wider. I tried to make the container 200px wider and changed several places without success. Perhaps the theme could have the width elements grouped in one place with comments describing their relationship. If we wan to add 200 or 260 px to the content then add it here, here, and here. The same for making the sidebar wider.

Here I made the overall container wider:

#container{
background:url(img/full.jpg) repeat-y top left #000;
width:920px;
min-height:700px;
margin:auto;
font:12px Arial, Helvetica, sans-serif;
}

and then made main and sidebar the proper width to compensate, added together totaling 920px:

#main {
background: transparent url(img/middle.jpg) no-repeat scroll right top;
width: 593px;
padding: 0 20px;
}

#sidebar{
height:100%;
color:#FFF;
font:12px Arial, Helvetica, sans-serif;
letter-spacing:1px;
text-align:left;
width:240px;
margin-right:10px;
float:left;

}

I just opened style.css and did a search for "width", and checked if each width element needed changing or not. Finally, I took Middle.jpg and widened it accordingly.

I am, however, experiencing the footer issue that you also posted and am looking into it.