@ theshyguy: The forum software only allows one attachment per post. The 1-1-1 rule is intended to prevent individual users from rapidly flooding the forum with single-sourced content (an act that could be construed as piracy and/or copyright infringement).
@ lebowquade: The 1-1-1 rule that Palomine mentioned limits you to one attachment per day in each thread. After posting an attachment, please wait at least 24 hours before posting another. Thanks!