Brahma Kapalam - Story of Lord Brahma's fifth head

LORD BRAHMA - creator of the world according hindu mythology 

vehicle- swan

wife - saraswathy devi - goddess of knowledge 

Even though Brahma is typically shown as having four heads looking in the four directions, legend holds it that at one time he had five heads, the fifth looking upwards. However originally he is said to have possessed just one head. At that time the cosmos did not exist and Brahma was self-contained and self-content. 
The husband of the Rathi Devi,Manmada was praying for Lord Brahma blessings then with the huge tapa of the Manmadh Lord Brahma was happy and gave him  a 3 arrows which when used on anyone will become more addicted to romance , then to test weather the wish given by  the god is working or not , he tried one of the arrow on Lord Brahma Itself.


However lord Brahma alone at that time was he eventually started longing for company. At this time, he split himself to form a female form, called Satarupa (the one with a hundred beautiful forms). As he laid his gaze upon Satarupa, Brahma immediately felt attracted towards her. To avoid Brahma's gaze, Satarupa tried to slip off in various directions but was unsuccessful as Brahma developed a head in each direction. Finding no other way, Satarupa start ascending upwards but then too, Brahma developed a head that looked upwards. Shiva noticed all that was happening. Since Satarupa originated out of Brahma, Shiva felt Satarupa was a daughter of Brahma and hence it was improper of Brahma to be obsessed with her. Shiva therefore cut off the head of Brahma that looked upwards so she could escape him. As an additional punishment for this unholy behavior of Brahma, Shiva cast a curse on him and directed that there be no proper worship of Brahma. Ever since, only Vishnu and Shiva out of the three Gods comprising the Trinity are worshipped while Brahma is almost totally ignored. It is also said that since then Brahma has been trying to redeem himself of his sins by continuously reciting the four Vedas. According to Shiva Purana, the incestuous union of Brahma and Satarupa resulted in the birth of Swyambhu Manu, who eventually turned out to be the progenitor of Man

Some might Ask Why Brahma who knows all vedas did a stupid thing of gaze on SataRupa 
the Answer for that is the Manmadha Was given a wish of having 3 Arrows which increases the lust of Romance in one so to test the given wish would work or not? Manmadha used one of the Arrow on Lord Brahma itself because of that Effect Lord Brahma was behaving unusually.



The Fifth Head when cursed by Lord Shiva Was cut with the trishul and the fifth head of the Brahma seperated from trishul In Badrinath and in that place the fifth Head of Lord Brahma got Mukthi so the place in Badrinath is Famous as Brahma Kapal and the rituals of pinda pradhan is done over here and its said that once if we perform pind pradhan in this place those people will get mukthi and those people will never get rebirth .
If once pind pradhan is done in this place no need to do in any other place for life long.

Here is the story for the question 

why Brahma is not having many temples like shiva and vishnu 

In spite of being one among the three gods forming the Trinity, worshipping of Brahma worship is not as widespread as worshipping of Shiva or Vishnu. In India, there are only two temples dedicated to Brahma, as against thousands dedicated to Shiva and Vishnu. One of these two temples is at Pushkar near Ajmer in Rajasthan. The other is at Khedabrahma in Kerala. It is believed that once Lord Shiva stood in the form of a great linga with no end under the ground or in the sky. Brahma and Vishnu threw each other a challenge of superiority in which one of the ends had to be reached. Brahma took the form of a swan and flew upwards while Vishnu turned into a boar and started digging into the ground. However, even after a lot of efforts, neither of the two found the end of the linga. However to exert his superiority, Brahma came back and lied to Vishnu about having found the top of the linga. Shiva flew into a rage as soon as Brahma uttered the lie and took his own form from the linga and cast a curse on Brahma and declared that he would never be worshipped. Further, since the Ketaki flower stood witness to Brahma's blatant lie, Shiva cursed the flower as well and since then the Ketaki flower is not used in religious rituals.

the above content is true as per my knowledge