In the world of Search Engine Optimisation you are likely to find the most commonly believed tip to getting top search ranks for websites is Keyword Density. However, getting this correct is important, but in your haste you may neglect a few things, one of which is your navigation.
As with most objects on the internet created with Flash (or similar third party software), creating a navigation with Flash will cause problems for some users and search engines. Search Engines struggle to index anything that is not HTML or XHTML (whether this is strict or transitional), SERPs cannot follow links within flash or any other third party script. In addition to this you are limiting your audience by forcing them to use Flash Player**, regardless of if this is previously installed or not it will take more time to load the HTML or XHTML.
(X) HTML and CSS
Unlike the solutions above, HTML and CSS are the best way to go. Using the unordered list
*Flash and Flash Player refer to Adobe Flash and Adobe Flash Player.