When I open the font identification forum, every profile picture of the questioner (especially for the recent subjects) are changed into a picture of skull. But strangely, profile picture of someone who suggest a font isn't changed. This is just me, or there are something wrong on font identification forum?

it's not a problem, and it's not about the identification forum.
it's the default avatar.
if a user wants to change his avatar, he has to change it on this page : http://www.dafont.com/member_pic.php

rayhan, keep in mind that many of the people who provide suggestions in Font Identification are also Dafont Forum Moderators, and I think most or all of them have chosen a custom avatar. In many cases, their skill at identifying fonts was a major factor in their being chosen as Moderators. Anyone can add a custom avatar to their profile, but most of the people who ask questions in the forums haven't added one. The skull serves the same purpose as the silhouette head on Facebook for people who don't use an avatar, just a 'place holder' for an image.

Wah, thanks for the information! I haven't been around this site for a long time. So I didn't notice some changes on the site like changing default avatar into skull. Before, I thought it was hacker, virus, or anything try to disturb this site.