Deep linking is creation of hyper link or a redirection that points to a specific page on a website . Click on Example link if I am a website of a company with lots of advertisements and hefty investment in getting my home page seams screen cracking I wont appreciate anyone linking my this URL because it redirects to a particular page and whole of my advertisements and money involved in Home Page goes sinking. Deep linking used to be considered as an unethical practice as it redirects user to another page or image in place of Website’s home page. The biggest trouble is that the HTTP is unable to identify any difference between deep link and homepage link. It also has a logic behind it as HTTP actually opens web for all for users to share web links across the globe. There were many disputes on deep linking including Microsoft and Ticketmaster & Tickets.com and Ticketmaster and the lateral has lodged Court cases against the formers. The first case went out of court settlement while in lateral case judge has ruled out back linking as illegal until and unless the ownership of link is clear. Hence now the back linking is no more considered unethical or illegal on the other hand it is promoted as it brings visibility to the linked website and hence improved page ranking .
Inline Linking also called as Piggybacking, hot linking, bandwidth theft as it is the use of linked object by the 2nd site of 1st website without permission. 2nd website said to have inline link (hence the name Inline Linking) where the object is located (i.e. server of 1st website). The Inline linking brings with it the Copyright issue because many a times the 1st website objects to the image of the site and hence court cases decides such infringement. The Inline linking is used in ad banners and earning per click banners which actually redirects the advertisement and image on the displayed site to the server of the publishers local machine. The hosting server company provides the number and the demographic details of the click to the publisher and hence the payments are released. Another Issue which arises due to these banners is sometimes the hosted server address comes visible to the user and hence the advertising company sees unapproved usage of there advertisements on other sites. The Google pay per content and advertising is also based on this link. A similarity between deep linking and inline linking is that both of these were considered to be illegal and unethical practice but now they are one of the core elements of world wide web.
Back Linking also called as incoming links or inward links or inbound links are incoming links directing towards a website this used to decide the reputation of any blog/website on the world wide web nowadays as the number of backlinks is directly proportional to the website popularity across globe and hence was in line of fire previously when the people in 90s started backlinking each others websites and so called fake SEOs used to lure the novice blogger by showing that fake backlinks will drive traffic towards the site. It used to be an important point in deciding the page rank of a website in the search engine and search engine indexing but these days with the change in logic it is not of much importance in terms of website ranking on search engines but is surely a traffic booster. In between all this a voice was raised by some of the experts that reverse backlinking be banned from the system as they create loops for search engines bots to confuse and misinterpret the search ranking but with the change in search engine indexing logic reverse backlinking is not of much importance.