If you're traveling to Iran, this link to info on women's dress in Iran may also be helpful, combined with information from the previous page on women traveler's dress in Islamic countries -- note that the Islamic dress code for women takes effect when your airplane crosses into Iranian airspace, according to this site.
The site's information, which covers women's dress in Iran for tourists and travelers, reads in part: "Obeying Islamic rules including Hijab or Islamic dress-code is necessary in Iran. However these rules are not observed very strict, especially for tourists and foreigners."
Info is supplied on clothing color (doesn't have to be dark), what to wear on your head (just a scarf or hat mostly covering your hair), how much of your body must be covered (no bare arms or legs) and about your feet (sandals and bare toes are okay).
Relax and enjoy your trip!
