Logger Pro (cmbl) files are XML based files. You can therefore view them in any text editor, although it may not be exactly clear what you are looking at/for. As such, a lot of programs, (for instance, web browsers and web servers) that don't know anything about the files assume that they are text, and handle them accordingly:
If you don't do anything on the web server or to your web browser, Firefox/Chrome will open a cmbl as "text" in the browser. If you have Logger Pro installed, Internet Explorer will open the files in Logger Pro, (although not without throwing a security message on Windows Vista/7,) but will render it as text if Logger Pro isn't installed, (or isn't installed as the file handler for cmbl files.) It is possible to force Firefox/Chrome to not open them as text, but it involves installing some browser extensions on every computer that views your site. Note that you can always right click on the page of code and choose "Save Page as..." or click on the link to the file and choose "Save Link as..."
The ideal solution is to set the cmbl file as MIME type "application octet/stream" on the web server, which will force the Firefox/Chrome to download the file instead of trying to view it in the browser. How exactly you set file types as that is very server specific, but here are some pointers:
There are other options. You can force Logger Pro to write binary files, (instead of text based ones,) which will also gets around this problem because the web server and browser will then see that the files are binary and will not try to render them as text. To do that you need to edit the UserSettings.txt file. On Windows that file is in the folder:
C:\\Program Files\\Vernier Software\\Logger Pro 3\\en-US\\Support
On MacOS the folder is in the application bundle, (Ctrl-Click on the Application and choose "Show Package Contents") in the Contents\\Resources folder.
In that file there is a line that says:
Change that to:
Then resave the file. (Note: Because of Windows security features you will need to save the file somewhere else, such as the Your Documents folder, and then move it to the Support folder after editing.) After you do that, any file you save (you'll want to open and resave any existing files you are distributing,) will be in binary, not text.
However, the easiest solution is often to just put the cmbl file in a zip file. If you are distributing a lot of files, (the entire Physics with Video analysis folder, for instance,) this is probably the best way to go anyways...