After uploading a media file i can enter a coordinate. There is a link to check it which has the form
http://www.openstreetmap.org/?lat=xxx&lon=yyy&moreParameters...

This is an old url format of the site. Furthermore a link with mlat instead of lat will produce an marker on the website, which is much better usable for checking the coordinates:
http://www.openstreetmap.org/?mlat=xxx&mlon=yyy for example http://www.openstreetmap.org/?mlat=50.7573&mlon=6.0947
I would suggest no other parameter for the link. The default choosen options will be ok.