Question: Is it permissible to kiss the Yemeni corner (of the Ka'bah)?

Response:
Kissing the Yemeni corner (ar-Rukn al-Yamaanee) is not confirmed from the Messenger of Allaah (sal-Allaahu `alayhe wa sallam). Any act of worship which is not confirmed from the Messenger of Allaah (sal-Allaahu `alayhe wa sallam) is an innovation and not something which draws one near to Allaah. So based upon this, it is not legislated for a person to kiss the Yemeni corner since this is not confirmed upon the Prophet (sal-Allaahu `alayhe wa sallam). Rather, it has been mentioned in a weak hadeeth that can not be used as proof.

Shaykh Ibn 'Uthaymeen
al-Bid'u wal-Muhdathaat wa maa laa Asla lahu - Page 388;
Fiqh al-'Ibaadaat - Page 348

Taken from fatwa-online.com