The .dar file is only the project file for DVD-Architect. It doesn't include any media at all. There's nothing in it you can see or hear. It only tells DVD-A how to create a DVD from your media files.

If you want to place your media files on a website you can open up the files in Vegas and render them to WMV or MPG or MOV format at lower bitrates.

If you really want the menues you've created to appear then you will probably have to play the prepared & burned disc in a DVD player and capture the output as a new video file, then render this to a web format. I don't know if DVD ripping software will capture the menus properly or not, but they might be worth a try. On the other hand, DVD menues are interactive, allowing the viewer to choose where to go next. It would be difficult and complex to maintain this interactivity in a web format file, so there might not be much point in putting the menues on a web page anyway.

If you only want to show what the menu screens look like then you could use the PrintScr key on the keyboard to capture DVD-A's preview window, paste the screen shot into a photo editor, crop it, and save the result as a still JPG file for posting on your site.