You can use FLV as video format, and make a flash video player to play the FLV file, the flash video player is a SWF file that can be embedded into web page with HTML embed tag. (
FLash OBJECT and EMBED tag)
<object classid="clasid:D27CDB6E-AE6D-11cf-96B8-444553540000" codebase="http://download.macromedia.com/pub/shockwave/cabs/flash/swflash.cab#version=7,0,19,0"
width="432" height="330" id="myMovieName" >
<param name="movie" value="myMovieName.swf" />
<param name="quality" value="high" />
<param name="bgcolor" value="#FFFFFF">
<embed src="myMovieName.swf" quality="high" bgcolor="#FFFFFF" width="432" height="330" name="myMovieName" align="" type="application/x-shockwave-flash" pluginspace="http://www.macromedia.com/go/getflashplayer">
</embed>
</object>
Making flash video player in Aodbe Flash CS3 will be technical, you can use this
web player Pro that will generate a custom flash video player for website and also provide a free video to flv converter.
For the bandwidth, it depends. If your streaming video will be visited by a lot of people, this will take much bandwidth.