When you publish a presentation with Articulate Presenter '09, each element of a slide is included in a .SWF file. If you build a presentation that contains a common element or background image on each slide without using master slides, that same element would need to be downloaded multiple times throughout the presentation. However, if that element is included in a master slide, it will only need to be downloaded once.
Please use the method below to create and apply master slides:
In PowerPoint, go to View > Slide Master.
Click a location in the slide thumbnail pane where you want to insert a new slide master and then click the Insert Slide Master button.
After creating the new slide master, you will see a master slide and several sub-slides that are built from the master. These represent your title slides and other layouts. If you want an image or a background to appear on each slide in the slide master, you will need to edit the master slide (the slide at the very top).
To apply the newly created master slide, go back into your Normal PowerPoint view, right-click a slide, and then choose Layout. Choose your slide master.
Here's a screencast on creating master slides in PowerPoint:
Here's a screencast on converting your slide elements into a master slide: