I need to place several markers which specified by coordinates on embed map. I know how to do it for one marker, but don't know for multiple.
<iframe width="100%" height="100%" frameborder="0" scrolling="no" marginheight="0" marginwidth="0"
src="https://www.google.com/maps/ms?msid=204293175747830583907.0005022420ef3bca6a816&msa=0&ie=UTF8&t=m&ll=40.79042,-73.945541&spn=0.462677,1.056747&output=embed"></iframe>
You cannot do this with the google maps iframe embed.
You either need to do it with Google Maps Map Maker (http://www.google.com/maps/mm) or you need to use the Google Maps API (https://developers.google.com/maps/).
The downside of the Google Maps Map Maker is you need to manually go back and recreate your map any time you want to make changes.
I would suggest using the Google Maps API.
This is a great little tutorial that shows you a simple Map with multiple markers using the Google Maps API - http://wrightshq.com/playground/placing-multiple-markers-on-a-google-map-using-api-3/