T and V
At any given time, your website's visitors should be no more than a single click away from watching graphic, gratuitous violence, or huge, bouncing boobies. These are the pillars upon which the Internet was based, and to deny them is to deny your site any chance of success.
Men exist to perform two acts: fuck women, and kill other men. The Internet exists, in the same way violent movies and videogames do, to satiate these desires. It is therefore not only a mistake, but an outright crime to the members of your gender not to put guns and asses and explosions and nipples and fistfights and belly buttons on every single page of your website. They are why we use the Internet, they are what we want, and they are why we exist.
Hell, even better: just combine tits and guns at every turn and save yourself some time and bandwidth. Show us half-naked chicks kicking the crap out of each other, or bikini babes shooting up terrorist caves with M16s. The website which includes DD girls killing zombies with samurai swords is a website worth visiting at least once an hour.
If you want highbrow, then turn off your computer.
Do the exact opposite of what we did yesterday
A lot of this comes down to simple web design etiquette, but don't use absurdly girly, clashing, vibrant colors. Don't turn your entire homepage into various shades of pink and purple. Don't turn your background into the internet equivalent of a disco ball at a gay rave. Don't spend the entire day talking about exactly one subject, and don't have that one subject be how awesome it is to make out with dudes.
Or male tanning, which I can now unironically say is FUCKING RIDICULOUS. Just watch the video on the sidebar at this site and tell me it isn't absurd to the point of being heartbreaking.
The heterosexuality of male tanning aside, however, pretty much all of you were horrified and/or barely amused at DoubleViking.com's flamboyant version, which should tell you a lot about how intensely awful and un-manly all the skills we used in its creation have the power to be.
Piss off your readers
Note that yesterday we threw flamboyant, vomit-inducing April Fools' fabulousness at you, and today you are back, reading this article. This is not a coincidence.
Think of it like a relationship with a woman: you must be alternately cruel and kind in order to retain the interest of those you care about. These moments of cruelty must be very rare indeed (a girlfriend would not tolerate you cheating on her every month, and our readers would eventually leave if we gave male cosmetic tips every Friday), but that hint of unpredictability -- that bit of confusion -- is necessary to any lasting relationship.
Not to suggest that you can't trust us, of course -- never will we highlight Fried Green Tomatoes as a movie Real Men Love -- but it never hurts to have a bit of randomness and spontaneity every once in a while.
Remain exactly one step away from outright pornography
As mentioned earlier, everyone loves nudity; however, everyone also loves the ability to surf websites at work without losing their jobs. Most companies are contractually obligated to terminate employees for looking at pornography using company bandwidth, so make sure your website does everything in its power to be titillating and boner-riffic, but without crossing the territory into actual pornography which will get your visitors shitcanned faster than you can say "2 Girls 1 Cup."
The sort of tasteful quasi-pornography which the best sites engage in -- and, obviously, I would include DV in this category -- stops just short of actual titsmanship. Most employers still go by the Jacobellis vs Ohio definition of pornography, which it to say, "they know it when they see it." So long as they don't see vulvas, penetration, or too many nipples, the visitor and the website remain safe (most advertisers don't really get off on supporting porno sites). Not that there's anything wrong with porn, and not that porn isn't inherently Really Goddamned Manly, but there's a time and a place -- it's called "the second you get home, before your girlfriend gets back from class."
Actually, with that in mind:
Remain exactly two steps away from illegality in general
Just because you're a man, doesn't mean you have to be a slave to THE Man. We citizens of the Internet love antiauthoritarianism (just ask all the Ron Paul supporters), and thus it is the job of any halfway decent manly site to stick it to said Man whenever possible, without getting shut down.
Level with your audience. For instance, they're undoubtedly gonna pirate stuff illegally off the Internet, so give them some tips -- but don't specify exactly what to do, or tell them where to get it. The FBI evidently hates that shit. Feel free to give tips on lying to members of the opposite sex, cheating at work or school, or committing crimes; just don't get so specific that Johnny Law can accuse you of fully teaching visitors how to do all the awful stuff we'd do anyway.
Welcome to the future, where the average attention span is shorter than the time it took you to read this sentence. We live in a digital world, and thus we require digital stimulus, especially when it comes to our favorite websites. Combine videos with pictures with flash games with text articles with pop-up books and virtual reality simulators: we all get bored easily, and the Internet exists to prevent that from happening at all costs.
Now, don't combine all the stuff into a huge casserole of media nonsense in the same way MTV does; they are the epitome of unmanliness in today's world, and should be distanced from whenever possible. Just don't relegate yourself to only being a video-posting blog, or only writing long treatises on human existence, or even only posting pictures of half-naked chicks.
We want tits, guns, sports, and cars, and we want them in as many different media forms as humanly possible.
That is what we need. That is what makes a manly website.