Clocking is a black hat SEO technique in which the content of the site reflects in 2 ways, it means the same content is looks different for the search engine and it looks different to the users, which is not good , the content of the site should be exactly same for the search engine and for the user ............ let me know Thanks
To be more specific cloaking is bad when you do it on a agent level, but not on a browser level. I am talking about responsive design.
I have grabbed some information from wikipedia on SEO Cloaking, go through: Continued: http://en.wikipedia.org/wiki/Cloaking
It is a method of presenting different contents based on determining IP addresses. e.g. Search engines with certain IP addresses will be shown a one version of a web page and all other IP addresses will be shown another version.
Cloaking is a search engine optimization (SEO) technique in which the content presented to the search engine spider is different from that presented to the user's browser. This is done by delivering content based on the IP addresses or the User-Agent HTTP header of the user requesting the page. When a user is identified as a search engine spider, a server-side script delivers a different version of the web page, one that contains content not present on the visible page, or that is present but not searchable. The purpose of cloaking is sometimes to deceive search engines so they display the page when it would not otherwise be displayed (black hat SEO). However, it can also be a functional (though antiquated) technique for informing search engines of content they would not otherwise be able to locate because it is embedded in non-textual containers such as video or certain Adobe Flash components.
Cloaking is one type of Black-hat technique in Search engine optimization, which are used to mislead SE by present altered contents for sufficient to search engine spider than the absolute one that is presented to end-user visibility.