This problem has arisen quite a bit since the release of SharePoint 2010. On the MSDN forums, there are many questions that seem new, but they always end up coming down to one setting. In SharePoint 2010, there is a new setting at the web application level called Browser File Handling (Fig. 1). You get to this setting with these steps:

• Central Admin > Application Management > Manage Web Applications
• Single-click the row of your web application
• Click General Settings in the ribbon
• Scroll down to Browser File Handling and select Permissive

Figure 1 – Browser File Handling settings

By default, this is set to Strict when creating a web application. However, this causes issues in many ways related to opening certain files from SharePoint. The most obvious example is with PDFs. When set to Strict, a PDF can only be Saved (downloaded), but in Permissive mode, the PDF can be opened directly. For instance, here are the different results when clicking on a PDF in a SharePoint 2010 Document Library:

Figure 2 – Opening a PDF in Strict mode

Figure 3 – Opening a PDF in Permissive mode

As you can see, in Strict mode, I am prompted to Save or Cancel (Fig. 2). In Permissive mode, the PDF immediately opens without being prompted (Fig. 3), and in my case, my PDFs open in the browser by default (this is a setting you can change).

Another way this issue manifests itself is when opening versions in an InfoPath form library. Someone posted this issue on the forums, and when I didn’t experience the same issue, I immediately thought of Browser File Handling. Mine was already set to Permissive, so I switched it to Strict, and I experienced the same issue. Switching back to Permissive fixed it. Here is the scenario:

Figure 4 – Form Library set to Open in the Client (not browser)

Figure 5 – Form Library set to Create major versions (max 2)

Figure 5 – Check the Version History of an individual form and click on an older version to view it

Figure 6 – Result of clicking an older version in Strict mode

Figure 7 – Result of clicking an older version in Permissive mode

As you can see, when in Strict mode, the browser views this as a regular XML file (Fig. 6) and doesn’t associate it with InfoPath like it does in Permissive mode (Fig. 7).