SMIL (Synchronized Multimedia Integration Language) allows audio and slides to be played back, in sequence, automatically. RealPlayer or Apple's QuickTime player (or similar) is required.
To listen to audio of the entire talk, make a choice from the sound menu (at left). Otherwise, select a section from the pictures menu and you will be offered the audio that goes with it (if available). You will need a player for the desired format (and speakers, a soundcard, operating system drivers, etc.). More help is available.
Select a thumbnail from the menu on the left; The large version will appear here. If the image is too big, you may wish to resize your browser window or adjust the width of the menu.