Click-through rate, or CTR, is the ration of users who click on a specific link to the number of total users who view a page.

CTR can also be applied to email, or advertisement and it is commonly used to measure the success of an online advertising campaign.

To work out a CTR the equation is, clicks divided by impressions equals CTR.

Currently it is nearly impossible to get an accurate measurement to judge the emotional reaction to a site, however, CTR is an easy piece of data to acquire and can allow campaigners to see how well their ads are doing.