Deleting file attachments

The easiest way to delete an unwanted file attachment is to open the reference (by double clicking on it), scroll down to the File Attachment field, highlight the attachment and delete it, then close and save the reference.

Transferring references with file attachments between EndNote and EndNote Web

There is currently a problem which means that if you try and transfer a reference that has a file attachment from an EndNote desktop library to your EndNote Web account and then back again, the file attachment will be lost.
EndNote are working to solve this, but for the moment it is best to avoid transferring references with attachments.