Can Flash banner ads be seen by everyone?

No. You need the Flash plug-in installed on your computer to see Flash banner ads. The plug-in is available for free from Macromedia. Most of today’s browsers have the plug-in preinstalled. Almost all Internet users can see Flash banner ads. Most ad serving technologies will first check to see if the correct plug-in is installed and, if not, serve a secondary banner ad such as a GIF banner ad that you provide along with your Flash banner ad.