Not many people in my industry are comfortable about the economic situation right now. But here is some good news : 2 out of 10 best jobs to have in a recession are still Software related.
Application cache (appcache) is a powerful feature in HTML5. However, it does come with baggage. Many (see links below) advocated ferociously against it due to tricky issues it comes with. For someone who is just testing waters, these issues may throw them off grid. Knowing them before hand helps reduce some unpredictable effects.