The <a href=httpsdevelopersfacebookcomtoolsdebug rel=nofollow>Facebook for Developers Sharing Debugger<a> page with a pointer to the first warning which notes that the image is too small
The <a href=httpsdevelopersfacebookcomtoolsdebug rel=nofollow>Facebook for Developers Sharing Debugger<a> page with a pointer to the first warning which notes that the image is too small