Sorry for the title but I'm drowning in options. I'm a beginner who is trying to learn html, css and javascript. I'm working on a sample page right now and want to create a simple navigation bar. I want the bar to be horizontal, span the whole width of the page and have that hover over effect in which it changes colors when I place my cursor over it. Some people tell me to use only html and css, some say do it in Javascript. I'm confused on which to use and then how to do it?

HTML & CSS is far more accessible

http://www.cssplay.co.uk/menus/final_drop.html
http://www.cssplay.co.uk/menus/index.html
http://www.seoconsultants.com/css/menus/horizontal/

I have heard that, but in doing research, it also seemed like javascript was better supported by more browsers, especially older ones.

Here's another place to get started
http://css.maxdesign.com.au/listamatic/

http://css.maxdesign.com.au/listamatic/horizontal02.htm
http://css.maxdesign.com.au/listamatic/horizontal03.htm
http://css.maxdesign.com.au/listamatic/horizontal04.htm

I believe Chris' recommendation was also based upon your statement that you are a beginner. Learning two things is simpler than learning three.

I completely agree and appreciate everyone's help. I'm learning web design so I can make a site for my business. I fear that many of my clients will be using older browsers so what will happen if their program can't display the css?

Some browsers can't display javascript, either (and some people just turn javascript off). Webpages also look differently on IE/Firefox/Opera/Safari/etc and on windows/linux/unix/mac/etc... do you test all those combinations at all resolutions? If you want to be THAT thorough it is possible and you could do what you want to do with a combination of both javascript and css to cover as many possibilities as possible... and there's still no guarantee that there wouldn't be a setup out there that it didn't work on.

You have to make choices. CSS is *widely* recognized and implemented. It's more likely to be available than javascript, in my opinion, so I would just do it with css.

#nav a {background-color:#cccccc;}
#nav a:hover {background-color:#333333;}