The purpose is that rows are dynamically added to a table and it is not as nice (and slower) to apply the rule manually later.

The specific example is that I am creating a tree table to represent a folder directory. Each folder is a div. In each div, there is a ul with an li for each columns' information. These li have a class name equivalent to the column name. This provides column width. I want to make the columns resizable however. I could do $('.className').css('width', newWidth) but then this wont apply to newly inserted items. Therefore, I want to modify the css rule. How do I do this?