Hi. suppose there is a site, eg www.domain1.com which hosts one of it's image (suppose logo.png) on different site, www.domain2.com (logo path goes as www.domain2.com/hosted images/logo.png) now www.domain1.com gets 5000 unique visitors each day. my question is, will these visitors also be counted by the 2nd domain, www.domain2.com? means will it effect the visitor number of 2nd site?
No it will not as visitors are only requesting a file from the 2nd site which contains no tracking what soever. Just the same way as when you open a .png on your computer. The request for the image file will appear in the server logs of domain2, but this doesnt show as a 'unique visitor' in the traditional sense.