3 Columns : Minima : Left and Right Sidebars

this Article from http://bguide.blogspot.com/2008/03/3-columns-minima-left-and-right.html

Article Series: 3 Column Step by Step Guides

Here are the steps to convert a default 2 column Minima template in to a 3 column template with two sidebars on left and right hand sides of the main post area.

(If you really want to understand what's happening here, read the article series Three Column Templates Explained.)

1) Add a new CSS id selector for the 2nd sidebar wrapper.

• Go to Layout -> Edit HTML
• Locate the #sidebar-wrapper section (Do a Find using your browser)
• Copy that full section and paste below the existing sidebar section (it doesn't have to below) and rename it to #left-sidebar-wrapper
• Change the float: $endSide to float:$startSide of this newly copied section (See the code snippet below)

#sidebar-wrapper {
width: 220px;
float: $endSide;
word-wrap: break-word; /* fix for long text breaking sidebar float in IE */
overflow: hidden; /* fix for long non-text content breaking IE sidebar float */
}

#left-sidebar-wrapper {
width: 220px;
float: $startSide;
word-wrap: break-word; /* fix for long text breaking sidebar float in IE */
overflow: hidden; /* fix for long non-text content breaking IE sidebar float */
}

2) Introduce a new div element, as a child of the content-wrapper, to be the placeholder for the 2nd sidebar

• Locate the
  element.
• Copy the code shown in red, above that section (this has to be above)

3) Expand the width of the other wrappers to accommodate the new sidebar

• Locate the CSS sections called #outer-wrapper, #header-wrapper and #footer
• Change their width property to 880 pixels

#outer-wrapper {
width: 880px;
margin: 0 auto;
...
}

#header-wrapper {
width: 880px;
margin: 0 auto 10px;
...
}

#footer {
width: 880px;
clear: both;
margin: 0 auto;
...
}

4) Do necessary adjustments to margins, padding etc

• Locate the #main-wrapper section
• Insert a left margin of 12 pixels.

#main-wrapper {
width: 410px;
margin-left:12px;
float: $startSide;
...
}

Note: Step 5 is only needed if your Layout Editor does not show the newly added sidebar. There was an issue where the Firefox browser didn't show a 3 column template fully in the edit mode. But Blogger reports that the issue has been fixed now.

5) Modify the CSS rules for the wire frame layouts editor.

• Locate the end of the skin denoted by "]]>"
• Add the following code above that line.

/** Page structure tweaks for layout editor wireframe */

body#layout #outer-wrapper {
padding-top: 0;
width:720px;
}
body#layout #header-wrapper,
body#layout #content-wrapper,
body#layout #footer {
padding: 0;
width:720px;
}

body#layout #main-wrapper {
width:400px;
}

body#layout #sidebar-wrapper,
body#layout #left-sidebar-wrapper {
width:150px;
}

]]>

Save the template. Switch to Page Elements view and enjoy your 3 column template!