How to change left width 2-columns skin of x-cart v4.5?

For our personal needs, we may need to change the left width of 2-columns skin of x-cart. At present, most users are using X-cart Gold V4.5.
Go to skin/2-columns/css, and open altskin.css, change:
#left-bar {
width: 207px;
margin-left: 0;
}

#center-main {
margin: 0 0 0 250px;
padding-bottom: 0;
}

to:
#left-bar {
width: 207px;
margin-left: 0;
}

#center-main {
margin: 0 0 0 307px;
padding-bottom: 0;
}

and change:

#header .line1 {
height: 30px;
margin-left: 250px;
width: auto;
}

#header .line2 {
border: 1px solid #fd9734;
background: url(../images/2column/header_bg.gif) repeat-x top;
margin-left: 250px;
width: auto;
}

#header .line3 {
height: 34px;
margin-left: 250px;
width: auto;
}

to:

#header .line1 {
height: 30px;
margin-left: 307px;
width: auto;
}

#header .line2 {
border: 1px solid #fd9734;
background: url(../images/2column/header_bg.gif) repeat-x top;
margin-left: 307px;
width: auto;
}

#header .line3 {
height: 34px;
margin-left: 307px;
width: auto;
}

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