File naming. We all do it differently on our own computers. With Windows and OS X we have a large amount of leeway in how we can name our own files on our own computers. This is normally not an issue. It becomes an issue though when we want to use some of those files on a website. This is especially true of image or video files, though it can affect anything from documents to archive files as well.
As opposed to how personal computers work, most servers are fairly strict in how a file must be named in order to have it work correctly as part of a web page. The strict naming of files for linux servers only allows for letters, numbers, underscores (_), dashes (-) and periods (.) to be a part of the name of a file. You also must name the file as a continuous string of characters without spaces, so “my image.gif” isn’t valid but “my_image.gif” or “myimage.gif” or “my-image.gif” are valid.
This issue is particularly important for usage of WordPress with my AWSOM Pixgallery plugin, since incorrect naming of the image files can lead to issues displaying the images. The plugin supports custom names, so once you upload your images you can input a caption/custom name in the admin menu in any way you wish for display purposes, just make sure you leave the actual file name as something that is acceptable on the server.