Depending on your support for web design and development at the new job, I would limit your content and headings to the system fonts that normally come stock with every computer: Arial, Helvetica, Times/Times New Roman, Georgia, Verdana.
Use pixels for measurement and sizing in your flat/graphic design compositions. Be mindful of your graphical resolution - 72dpi is standard for screen/web.
Checkout tutorial websites like http://www.tutorialized.com for web design, web, 2.0 and Photoshop tutorials to get a quick run-through of how to create common effects (if that's what you're going for).
Think about who the target audience is as well. This will help with determining just how large or small you should make your text, as well as how wide you can make the design.
Most people like a medium size font on the web today, but an older audience may appreciate larger text. With regards to width, screen resolution of your audience may eventually affect how the final product will be displayed to users -- if it is too wide, portions of the design will be off screen.
Incorporate these items into your work and be sure to explain your design choices to your interviewers. They should appreciate your attention to detail and the thought you put into making the design for the user/customer.