1) If you look into the html output, you will be able to see that those three sideboxes heading that you wanted to be presented in white are all within a <lable> element. If you look into line 54 of your stylesheet.css, you will be able to see the settings for the <label> element. I suggest you to take out the label from the group and start a new one like:

label {
color: white; font-size: 1.1em; }

2) To enlarge and center the heading, you can add the following to your stylesheet.css file. It should work.

h1#indexDefaultHeading {font-size: 1.6em; text-align: center;}

3) for the category listing on the footer, please let me come back to you in a min. (The bus had just arrived).