Actually don't delete anything, that file is a security file that blocks outsiders access.
It is obvious that a file like ../amfphp/browser/index.html should have some sort of protection. In order to access it you have to log through ftp , so log on thorough ftp on site, browse and open the file and it will work and safe
That file should be deleted. It is only meant for local testing use. htaccess files are not necessary and interfere with gateway calls. External access to the gateway via AMF can be controlled in the cross-domain policy XML file.
If you really want to keep the service browser on your production machine, then consider using htaccess for the browser directory only, but not the parent amfphp directory. However, this is still a security risk and I don't see why you would do it.