Both ways will work, but you should look into learning CSS; the plain advantage is that you can control all of the design in your website from one stylesheet.
If you're doing websites for clients, CSS is a must; clients will always come back to you after the design has gone from concept to actual HTML website and say things like 'Uh... We decided that we want the left menu in pink instead of blue - sounds easy, should only take you 5 mins.' - when actually, it means going through every page in their 100 page website and changing the HTML. With CSS you avoid this because every page takes the style information from the 1 file - hence only one update.
If you're doing websites for clients, CSS is a must; clients will always come back to you after the design has gone from concept to actual HTML website and say things like 'Uh... We decided that we want the left menu in pink instead of blue - sounds easy, should only take you 5 mins.' - when actually, it means going through every page in their 100 page website and changing the HTML. With CSS you avoid this because every page takes the style information from the 1 file - hence only one update.