If you wish to learn web design, then perhaps relying less on Photoshop may help you. Many web designers use Photoshop for layouts and various graphic applications, but how you use it should really depend upon what software or design you plan on coding the layout into (Wordpress, Joomla, vBulletin, straight HTML, etc.,). If your website is powered by a PHP script like mentioned above, even though all scripts use some sort of template system it can affect your design outcome and what you would be able to do. So its best to always be mindful of this.
Were you going for a breakup in the "pages" with changing the colors on each one? Would this be a layout for a responsive type of site where the backgrounds can change frequently? If you are using Photoshop to get a basic idea of where your layout would be, that is fine (extra work but that's up to you). Personally putting EVERYTHING into the Photoshop mock-up does not make a lot of sense.
For me I approach creating a new site kinda half and half. Half in Photoshop creating the graphics needed, buttons, logo, backgrounds etc., and the other half in a HTML editor hand coding the templates and how they will use the graphics I've created. It's just far more work to create a mock-up in Photoshop and then try and code it into whatever platform you are using IMHO.