MATURE FILTER FAQ

"Moderate: Choosing Moderate will mark your work as Mature Content, and deviants who have their mature content filter on will be met with a warning page. They can still choose to view your work, however.
Strict: Anyone under 18 will not be able to view your work. Keep in mind this does not mean you are allowed to post obscene material such as pornography or other content forbidden under deviantART's Terms of Service.
Mature Content Types
DeviantART provides optional flags that can be applied to mature content deviations to give the viewer a better idea of what the work contains.
Nudity: If your work contains nudity, revealing the genitalia of a model or character, you should assign this tag.
Sexual Themes: References to sex or overt sexuality, including sexually based humor. This category also covers images in which the character or model has taken a sexually provocative pose.
Violence/Gore: This refers to overtly realistic bloody or violent imagery, generally associated with horror and macabre, but can also apply to photojournalism or written work.
Strong Language: Can be applied to deviations containing profanity, vulgarity, and otherwise coarse or offensive language at the discretion of the submitter.
Ideologically Sensitive: If your work may be construed as offensive toward a person or a group of people due to a religious, political, social, or other belief please utilize this tag. This does not mean you are permitted to submit hate propaganda or hate art, which strongly implies and encourages violent acts against any of the above individuals or groups.
Submissions depicting nudity are allowed providing that the model is eighteen (18) years of age or older and providing that the image is not determined to be obscene or pornographic as detailed elsewhere in the FAQ.

All images containing nudity must be tagged as Mature Content upon submission. The deviantART staff reserves the right to mark any work with a general mature content tag if it is deemed by that staff member to require one."

This is in the dA rules, and yet there is still sexual art everywhere, along with extreme violence and language. To an extent, these are allowed on dA, but USE THE FILTER.
AS for porn...

"We do not allow the submission of "Adult" or pornographic materials to deviantART under any circumstances. Such material will be removed immediately as it comes to our attention.
You are not allowed to post outside links to any website which hosts pornographic content.
When we mention 'pornographic content' in our policies we are specifically referring to specific subjects which we will clarify below.

We apologize if the descriptions below are slightly graphic.

The following contents are considered unacceptable for submission in either visual art or literature form and will be subjected to immediate removal without notice.

• Masturbation
Hands should not come into contact with genitalia in a manner which is clearly a display of fondling or masturbation.

• Sexual Intercourse.
Subjects should not be depicted in a clear display of sexual intercourse. This includes depictions of sexual penetration, oral to genital contact, genital to anal contact, and oral to anal contact without exception. Some depictions of same sex genital to genital contact and some depictions of oral to breast contact might qualify under this guideline as adjudicated by staff but not all will be considered an automatic violation of policy.

• Vaginal, Penile or Anal Penetration
This includes depictions of any object being inserted into the vagina, penis or anus.

• Sexual body fluids (actual or simulated).
There should be no depiction of semen or vaginal lubricants.

• Erections.
There should be no use of imagery depicting a male erection, however there may be exceptions granted to illustrations created for legitimate medical or educational purposes.

• Vaginal or Anal Spreading
Female subjects should not be depicted with their labia spread or parted in any manner by hand or manipulated open or parted by any other artificial means or object. Neither sex should show the anus manually opened in a similar fashion.

• Adult oriented (sexual) toys.
"Adult toys" consisting of dildos, strap-ons, vibrators, and similar items which are crafted to realistically represent a phallus or "receptive" vagina are not allowed. Items and devices which do not depict a male or female organ in a realistic fashion will be reviewed on a case-by-case basis for acceptability in a submission. "


THE ITEMS IN QUOTES ARE DIRECTLY PASTED FROM THE dA FAQ
So start following the rules, okay? For the people who actually care?