You want your scenes to appear in a good light right? This tutorial will show you how to set up directional lights, point lights and spot lights.
<DirectionalLight id="directional" direction='0 0 1' on ="TRUE" intensity='1.0' shadowIntensity='0.0'> </DirectionalLight>
<PointLight id='point' on='TRUE' intensity='0.9000' color='0.0 0.6 0.0' location='0 10 0.5 ' radius='5.0000' > </PointLight>
<NavigationInfo id="head" headlight='true' type='"EXAMINE"'> </NavigationInfo>
<SpotLight id='spot' on ="TRUE" beamWidth='0.9' color='0 0 1' cutOffAngle='0.78' location='0 0 12' radius='22' > </SpotLight>
If you want to include lights directly in your x3d file , you need to use "DEF" instead of "id".
A scene with all three light sources could look like the example below. You can see a white directional light, a yellowish point light and a blue spot light.
For further informations about the lights, their attributes and implementation details please read the x3d specification.