Produced by brand and digital agency Rufus Leonard, ' has been devised to raise awareness of how cancer can affect sexual relations between couples.
The humorous film, shot in the style of an amateur self-help video, shows an American sex guru giving advice to viewers.
In it, she calls in her assistant, Roger, who she explains will use his finger to demonstrate how he can heighten her sexual pleasure.
He moves his finger out of shot and into the vicinity of the guru's lap and his arm begins to move rhythmically.
The film cuts to a series of metaphoric images of the guru walking through a Zen-type garden of paradise, before returning to the action between the guru and Roger.
"We're going to take a closer look now so you see exactly how skilfully Roger pushes the right buttons," she says.
At this point the camera pans down to reveal that Roger is using his finger to navigate a laptop computer.
"Just a couple more taps," the guru says. "A little to the left. And, yes! ." Viewers are then shown the website address.
The viral's launch coincides with the publication of Macmillan-conducted research into cancer and sexual relationships, in which 72% of respondents said cancer had affected their sexual relationships.
The campaign has also garnered the support of agony aunts Denise Robertson and The Sun's Dear Deidre -- who are offering advice on the site.
Michelle Rowley, a campaigns manager at Macmillan, said: "After finishing cancer treatment, a person's confidence can be shattered, their body image low and it can be emotionally or physically difficult to get intimate or have sex.
"It's well known that us Brits find it difficult to talk about sex and that many people turn to the web to look for advice.
"A light-hearted viral seemed a good way to break the taboo and let people know there is help and support available."
The viral was written by Helen Jones and directed by Delinquent's Jason Glenister.
Gietta Gudge, who was diagnosed with breast cancer in 2004, said: "Trying to keep our physical relationship active was one of the worst things I had to go through during and after my cancer treatment.
"I had no idea that my body and emotions would be affected the way they were. If I had been spoken to about the effect my cancer and treatment would have on our sex life at the beginning, I believe we would have been better equipped to cope with it all."