By default regions are all equal widths. For example, say you have a page with a single region:
If you add another region to the right of the existing region, each region will take up 50% of the width of the page:
If you want the regions to take up a different amount of space, you can explicitly set the width of each region. You can set the width of a region to a specific number of pixels, or to a percentage of the overall width of the page.
You can also set the height of a portlet or item region to fit the content that will be included in it.
To
change the height and width of a region, you must have at least one
of the following privileges:
Manage All privileges on the page group to which the page belongs
Manage privileges on the page
Manage global privileges on All Pages
Go to the page with which you want to work.
Switch to Edit mode.
Click 
in the region for which you want to change the width.
In the Width field, enter the width of the region in pixels, or as a percentage of the overall width of the page.
Note: You must include a percent sign (%) if you want the number you enter to be interpreted as a percentage, rather than a number of pixels.
In the Height field, enter the height of the region in pixels.
Click OK to return the page.
If you choose to have the width of some regions expressed in pixels and others on the same page expressed in percentages, the page may be look slightly different in different browsers.
Even if you enter a height or width of 1 in an attempt to make the region as small as possible, the region will expand to display the full contents of the region.
If you add another region to the right or left of an existing region, the region widths are automatically reset to be equal. For example, if you have a page with two regions, one with a width of 40% and the other 60%, if you add a third region, all the regions will be reset to a width of 33%.
You might have a region configuration that looks something like the following:
In this case, even if you set regions 1 and 3 to have different widths, the actual width of the column will be as wide as the widest region in that column. So if region 1 had a width of 40% and region 3 had a wdith of 20%, when viewing the page, the column containing regions 1 and 3 would be 40% of the width of the page.
Pixel widths have a higher precendence than percentage widths. Therefore, if region 1 had a width of 40% and region 3 had a width of 200 pixels, when viewing the page, the column containing regions 1 and 3 would be 200 pixels wide.