Resize and center a Purpleshade template

[mikajlo]

Hi, I am using a purpleshade template for ZC 1.3.5. It is designed with width=100%, but I would like to resize width of template to 750px. I manage to do it with:
#mainWrapper {
/* background-color: #ffffff; */
text-align: left;
position: center;
width: 750px;
vertical-align: top;
}

but now whole template is left aligned and I want it to be in center. Also Header section must be resized to 750px and aligned to center. I want it to look something like Classic template, nerrowed to 750px and centered in horizontal alignment.

Thanks.

[clydejones]

Make the change in the highlighted portion:

#mainWrapper {
/* background-color: #ffffff; */
text-align: left;
margin: 0 auto;
width: 750px;
vertical-align: top;
}