Content box beside box , need help

Hi,
Please visit this link
http://codex.wordpress.org/Custom_Fields
When you went there , there is a box “Contents” with :
1 Function Reference
2 Usage
3 Displaying Custom Fields
4 Advanced Techniques for Custom Fields
4.1 Getting Custom Fields
4.1.1 Implementation Details
4.2 PostMeta Functions
4.2.1 Internal Functions
4.2.2 Template Functions
5 More Information and Resources

Once we click on these text we can quickly move to content we want to read . I want to do the same thing with my blogpost , any idea how to do it ?
Thank u , appreciate if someone let me know what kind of plugin I can use .