BAGHDAD, Iraq (CNN) -- A video posted on an Islamist Web site apparently shows two Iraqis being beheaded on a city sidewalk as pedestrians and vehicles pass by. The video was posted on a Web site that previously has shown video verified as being produced by a group led by Abu Musab al-Zarqawi. However, CNN has not confirmed the authenticity of this video. In the video, the two men tell their kidnappers that they drove truckloads of food and supplies to an American base in the central Iraqi town of Ramadi. The men said they lived in the Sadr City...