There is a rule that almost completely prohibits lemons on DA. Any fanfiction with any sexual content a.k.a lemons, will be considered unacceptable for submission if the reviewing staff of DA determines that the work possesses no redeeming literary qualities. Such as:

• Sexual Intercourse

A literary work may not detail graphic or explicit sexual intercourse. This includes descriptions of sexual penetration, oral to genital contact, genital to anal contact, oral to anal contact and may also include certain types of genital to genital contact and oral to breast contact.

This prohibition extends to descriptions of bodily fluids associated with sexual acts such as semen and 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.
Submissions which are judged to be in violation of these guidelines will be removed without prior warning.  Users found submitting such content may have their account banned or suspended without warning. Also be aware that we prohibit providing any outside link to another website which provides access to the material described above.  

Every artist who writes anything of this nature could potentially have their work taking off the web or suspended from DA. So stop this violation and sign this petition [link] to protect artisans from having there work  deleted and having there accounts banned .

(This is a journal entry on a member's page, requested to be placed here. I support this petition as I know of many stories that involve such materials that are excellent works regardless, and it would be a shame to lose those.)