column-width

The column-width CSS property suggests an optimal column width. This is not a absolute value but a mere hint. Browser will adjust the width of the column around that suggested value, allowing to achieve scalable designs that fit different screen size. Especially in presence of the column-count CSS property which has precedence, to set an exact column width, all length values must be specified. In horizontal text these are width, column-width, column-gap, and column-rule-width.

Values

<length>
Is a <length> value giving a hint of the optimal width of the column. The actual column width may be wider (to fill the available space), or narrower (only if the available space is smaller than the specified column width). The length must be strictly positive or the declaration is invalid.
auto
Is a keyword indicating that the width of the column should be determined by other CSS properties, like column-count.

<!DOCTYPE html>
<html>
    <head>
        <style>
            .myCSSStyle {
				-moz-column-count:4; /* Firefox */
				-webkit-column-count:4; /* Safari and Chrome */
				column-count:4;
				/*column-width: 100px;*/
				-moz-column-width:100px; /* Firefox */
				-webkit-column-width:100px; /* Safari and Chrome */
				}
        </style>
    </head>
    <body>
        <p>
            <b>Note:</b>
            Internet Explorer and Firefox do not support the columns
            property.
        </p>
        <div class="myCSSStyle">
            On the Insert tab, the galleries include items that 
			are designed to coordinate with the overall look of your 
			document. You can use these galleries to insert tables, 
			headers, footers, lists, cover pages, and other document 
			building blocks.
			
			When you create pictures, charts, or diagrams, they also 
			coordinate with your current document look.You can easily 
			change the formatting of selected text in the document 
			text by choosing a look for the selected text from the 
			Quick Styles gallery on the Home tab. You can also format 
			text directly by using the other controls on the Home tab.
            Most controls offer a choice of using the look from the 
			current theme or using a format that you specify directly.
			
            To change the overall look of your document, choose new 
			Theme elements on the Page Layout tab. To change the 
			looks available in the Quick Style gallery, use the 
			Change Current Quick Style Set command. Both the Themes 
			gallery and the Quick Styles gallery provide reset commands 
			so that you can always restore the look of your document  
            to the original contained in your current template. 
        </div>
    </body>
</html>