Start editing the spatial style sheet
A spaced style sheet is a good starting point for custom editing your CSS. In the space style sheet, contains all the elements you can modify. When you edit the space style sheet, the modification of the space style sheet will only be effective for the space you modify, and will be applied to all space pages. Create some styles in a space style sheet, then test them, and when there are no problems, you can apply these styles to the entire site. You can then make more customizations to Confluence's CSS including tweaking the search page, the main panel, and other general pages.
Use the right tools
Confluence's CSS is also quite complex, and web development tools will help you understand how a page's stylesheet is created. For some specific cases, you may need to look at the source code that already exists for the page. The following free tools will help you debug and view source code. h as the following free applications will allow you to do this.
1. Firebug
Firebug is a plug-in for the Firefox browser. This plugin allows you to view the stylesheets of elements in your page. This tool is very useful for analyzing your stylesheet for the current element, such as the one that applies only to the header.
2. Web Developer
Web Developer is a plugin for Firefox that allows you to edit CSS and create a new design directly in the page.
3. CSS Edit
CSS Editor is a standalone editor for Macintosh system editing using CSS. This editor takes all the current CSS style sheets and allows you to re-edit them.
Start with simple elements
You can start with some simple original edits and go through these edits to see how the modifications work. When making changes to CSS, you should check the effect of each change, which will help in better analysis and problem solving. Note that some pages may have elements that are more suitable for editing than others. For example, adding a gradient to the toolbar for a page can make CSS work better without breaking the page rather than changing the width of the entire page. Editing appropriate static elements, such as background images, is more accurate than designing the entire program or using JavaScript to display the drop-down menu (in fact, it is not recommended to use JavaScript to make too many changes).
https://www.cwiki.us/display/CONFLUENCEWIKI/Basic+Styling+Tutorial