The link to the online listing has been taken down, but not before the guys over at WCCF Tech managed to get a screenshot. Unfortunately there was no image of the Titan, but there were a few confirmed specifications.
For starters, the name 'GeForce GTX Titan' was used in the listing instead of the branding that some other websites used, the GTX 780. As we have read from the rumors, the GK110-based consumer GPU will simply be called the GeForce GTX Titan.
Some other information that was seen on the screenshot included a confirmation of the 6 GB of VRAM, PCIe x16 3.0 support, and a max resolution of 2560 x 1650. Regarding the resolution, one would expect that the card would have 4K support, but it shouldn't come as a surprise if we get a firmware update later along to add this. Gigabyte has already patched some of their boards to support 4K through dual Thunderbolt.
Earlier rumors indicate that the card might outperform the GTX 690 and will have a TDP of 235 W.
The price that the Asus GeForce GTX Titan was listed for on Proshop was €900, equal to about $1300 by current exchange rates. This is a fairly hefty price tag, but considering this is an early listing it wouldn't be surprising if the price drops to $899, or remains at about €900 for the European market, or both.
Availability is rumored to be between the 24th and the 26th of February, just moments away.