Change a Form's CSS Style on Click?

[MrSparkle]

I'm trying to create a similar effect to what is found on the top of Virb.com where a text form changes its style (background, font coloring) when somebody selects it. I can style the form manually using CSS, but I need a way to swap styles when a user selects it. Bonus points if anybody knows how to remove the text when somebody selects on it, but replace it if they don't fill in the field. Again, a similar effect to what is displayed on the site already.Thanks in advance.