Arduino Ethernet Board Hardware Problem

Typically decoupling caps are ~100nF - I'd be inclined to think these are tank caps for the power supply instead.

Regardless, it doesn't matter whether you use polarized or non-polarized, as long as the orientation is correct :slight_smile: You could use 10uF ceramics, which are (almost always) non-polarized, or you could use 10uF aluminum caps, which are (usually) polarized.