Hi Friends,At present i start Social Media Promotions for my website(Twitter.com). While i am promoting the site i am getting the followers. But after some time they are unfollowing me. I am doing the social media promotins personally only not by any 3rd parties. Can some body help me why they are unfollowing me.

That's just the nature of social media promotions, you will always have followers and unfollowers. If people find no value in your posts, they will unfollow you.

As a rule, people do not like it if they get spammed with advertisements or promotions all the time. Also, if you keep posting frequently, it also looks like spam.

Yes i will agree with you Ewald Horn.we will always have followers and unfollowers. And i didn't agree with you in this point "If people find no value in your posts,they will unfollow you". This may be the correct point. But i tweet regularly. And i am updating my profile with fresh and unique content.
I think it may have another reason.I am searching for the reason.

Try to follow back your followers that are related to your niche to retain them. Sometimes a 'follow' might mean 'follow me back'.