I'm using Mozilla for the web page video host, I guess ( may not be using the right word (host) ). Movie Magix Pro 16
Not much to go on Michael, but I wonder if possibly you have been saving a '.MVP' Magix project, rather than doing 'File' >> 'Export movie' >> and picking a video format suitable for your web page?
Are you wanting to host a file that others can download via FTP,? Do you have a file that does work from FTP? What is its file type / extension?
For me, web page videos are 'magic' not 'Magix' -- most I've seen are clips that are uploaded to places like u-tube and the web page just has a link to there. I think Mozilla is a browser not a host. A user needs a browser (program to display web content) on their own computer and somewhere else, not usually on an individual's computer, are hosts (big systems with massive storage and very fast processors) that send out the content when requested by a browser.
Following on from the previous answer, you will find that exporting your video suitable for Windows Media Player will give you the smallest file size and is preferable because the majority of computers have this player.
You may find that the file size of your video still exceeds your broadband host's permitted file size limit and you may find for a 2½minute video you could go over 5KB which is often the file limit on basic web space. In this case your best idea is to try reducing the resolution size to 240x180 or the bit rate to 96 or even both.
As for FTP, you will probably have been given your own personal webspace by your broadband supplier and their website will have advice on uploading files.