For those of you that are wanting to use .flv files in your sites you will need to add the mime type into your Plesk control panel in order to resolve the http 404 error. To add the mime type you will need to log into your Plesk control panel and click on the Web Directories icon. Once there you will need to click on the Mime Types tab at the top of the screen. In the field where it asks for the extension you will need to enter ".flv" without the quotes. Below that you will find a content drop down box that says "Custom" by default. Leave this as Custom and in the field to the right you will need to enter "flv-application/octet-stream" without the quotes. This will register the flash video file extension for your domain and allow you to use the flash video content in your pages.