You may have first learned about this website from either a glimpse of HRG's business card shown in HEROES, season 1, episode 12, "Godsend", or from the Primatech Paper banner ad on the HEROES NBC site (click the first image for a larger view):

The site is part of "HEROES 360", which is NBC's way to share bonus information about HEROES. One of the fun "get to know you" deals at this Primatech Paper site (owned by NBC), is a "career" form that you can get to when you enter the code, "mt36" (which code is received after texting the word "APPLY" to 46622), on this "Jobs" page. Some people think that the "36" in the code refers to the 36 people that are "on the list", or those that Chandra Suresh's program has identified as ones possessing some extraordinay abilities.
On the form page, it states, "Primatech Paper uses a sophisticated personality inventory based on the DSM-IV to help us determine if applicants fit our employee profile." It's thought that nbc might actually use the answers to learn more about the HEROES fans/viewers. Another reason for the form is to give people with either the correct combination (or possibly correct range?) of answers a clue to learn more, which came in the form of an email or text message.
Another way to get the clue, with a similar message, without giving out your email address or using a cellphone, is...
Although this trail was first published online the day before (or in the case of some fortunate HEROES viewers in Canada, the day of) the last new episode before first mark for HEROES News, since you may favor following an actual trail instead of visiting just one mark where I simply added a bunch of links.
So, besides the new episode descriptions (if a new episode airs) that you can read every Friday from the NBC Primetime Schedule at nbcumv (and I've edited the search details a little, so it'll look different compared to the nbcumv list at the next mark) at least 2 weeks before the airdate (unless a "sweeps" week and/or month is coming up, and then the listings are given earlier), you can also read an episode detail usually a little less than 2 weeks earlier than an airdate from the TVGuide HEROES episode list.
This compilation is of most of the instances of the "symbol" (or what I had erroneously called the space between the CTAGs) that are mostly from Isaac's paintings (with other instances in other images to follow). If you look at the code that was shown on Mohinder's monitor (from information on the flash drive that Eden found), you'll see that the shape is made from the plus signs that I non-technically thought were placeholders to fill the space between the CTAGs (where c, t, a, and g are the dna bases). Some bigger, though still blurry versions of the code are here or here. The following images are the screencaps with the symbols labeled to provide an unofficial count. Labeled Screenshots of the symbol (part 1): 
However, Tim Sale said he did not draw or was told to draw Uluru based off of any existing characters, so some speculation I had that some villainous character could make (what looked like in the painting) Hiro imagine that a monster from his comic books was going to fight him was incorrect. Jimmy Jean-Louis said his character (the "Mysterious man") had the power to erase people's memories, so I thought maybe he could do other "Jedi mind tricks" or had other "psy-ops" abilities to make people see what's not there, or not see what IS there... But that speculation would have been good only if it was Hiro with "Uluru" and if Uluru was drawn because it was from Hiro's recollections of the alien in X-men #143. And moving on... Below is an interesting set of shots. The first is of Hiro when he started to teleport from the subway to New York, and the second shot is after he saw some unfun stuff in a future New York setting and made a hasty retreat back to (about the time) when he first left the subway: 