Modern web browsers like Safari use a lot of helper apps, separate programs that let them know what to do with unusual file types like an .mp4 movie or, in this case, a portable document format (PDF) file. Normally it works fine and most people end up using Adobe's PDF Viewer plug-in for their Web browsing, letting you easily click on and view PDFs to your heart's content.

Except sometimes when there's a glitch in how things are set up in Safari on a Mac OS X system.

For reasons that I really don't understand, what appears to be the case is that Mac OS X ships with a broken PDF plug-in, but even with the very latest system patch, the problem's still present. And here's what you see...

Instead of viewing the PDF document in question, it's just a gray screen:

To say that's frustrating is an understatement! When I first hit this problem, I just switched to a different Web browser entirely, which is rather a dramatic solution if you think about it.

Instead, let's fix it.

To do that, use Spotlight to find a plugin called AdobePDFViewerNPAPI.plugin. Simply click on the magnifying glass icon on the very top right of your screen and type in that plugin name:

Click on "Show All In Finder" (since there should only be one) and you'll see this:

Delete the plugin. No, really. You'll see, it'll work because Safari actually has a built-in PDF viewer capability that doesn't need the Adobe software available:

That's it. Now quit and restart Safari and go back to the very same PDF URL and...

Why there's a broken plugin included with Mac OS X I cannot explain, but this'll fix things and you'll be good to go, no gray screen of non-viewing, just happy PDF files.