Using images and sounds for materials that are published on the internet means these materials must be created or stock. A source for sounds that can be used are on Sharecg. Usage rights for content on Sharecg are Limited use with credits, Non-commercial use only (many of these sounds created by people who can provide commercial licensing), and Unrestricted use. Sound Categories include: Audio FX, Digitally Produced Music, Executive Interviews, Industry Event Coverage and Interviews, Instrumental, Movie Score, Vocal and for everything else (Other).
Using good sound effects in videos or flash changes the overall quality of the production.