VIA Technologies P4X266-PE11-L User Manual page 40

Hardware Installation
2.5.16 DIMM and PCI Standby Power LEDs
DIMM Standby Power LED
PCI Standby Power LED
Important:
Lighted LEDs serve as a reminder that you must power-off the
system then turn off the power supply’s switch or unplug the
power cord prior to installing any memory modules or add-in
cards.