When using an LCD projector with a laptop to display a web page containing embedded video, the video shows up on the laptop, but not on the projected image on screen. According to "Projector People", the reason for this is:

" In most cases, Windows will lock out the ability to display motion video in two locations simultaneously because of the excessive resources needed. To bypass this, here are three options:

You can toggle off your laptop screen entirely so the projector is the primary display device. (usually FN + F8 or F10)

The other option would be to open a generic Windows media player prior to opening/starting your presentation. Windows will lock focus its lock on that one player, thus freeing up all remaining resources to display your true video/presentation.

Most video card manufacturers offer frequent driver updates. Search the manufacturers web site for updated drivers to your video card. Often there are new options included that can override the Windows lock.

See their Tips for Presenters page also