Google Presentations advanced features require authentication for getting access, like: if you’ve published a presentation at Google Docs, you'll receive a simple URL to view the presentation online. But, if you view the URL, Google will ask you to log in. To view the presentation without logging in, click on the small link from the bottom of the page: “View published presentation in a new window”.
If you want to link directly to the presentation and skip the authentication page, just add "&skipauth=true" to the URL provided by Google and replace “Presentation” with “Present”.
Here's an example:
URL provided by Google: http://docs.google.com/Presentation?docid=ID
Modified URL: http://docs.google.com/Present?docid=ID&skipauth=true
(replace ID with the presentation's ID)
Most people will also want to download the presentation, but Google doesn't offer this feature in the view-only interface. You can link to the PPT file by using this format:
Google, Google Docs, Google Presentation, Tips, Tricks