To Pray in a Dress/Place Subject to Khums
 Prayers performed in a place or in a dress, which was subject to khums but they did not pay it, is valid if they were unaware of the fact that these things are subject to khums, or of the rule of making use of them.

To Pray with an Imported Leather Belt 
As to the leather belt imported from non-Islamic countries, if one doubts whether it is made of natural leather or not, it is pure and there is no problem in performing prayers with it on. But, if one knows that it is made of natural leather but doubts whether it is from an animal that was ritually slaughtered or not, even though it is ruled as pure, it is unlawful to pray in it. Nevertheless, the prayers performed in the past are considered valid and there is no need to make them up if one did not know this ruling.

To Pray with the Bird's Feather 
The feathers of all birds are pure. However, if it belongs to a bird of inedible meat as per shar', to have it with yourself during prayer invalidates the prayer.

A Woman's Unveiled Hair during Prayer
If a woman's hair is unveiled unintentionally but she immediately covers it upon realizing that, her prayer is valid.

To Cover the Feet in Prayer
During prayer, a woman should cover her whole feet in front of a non-maḥram. In case, there is no non-maḥram, it is not necessary to cover them up to the ankles.

To Cover Artificial Hairs 
During prayer, it is not obligatory for a woman to cover her artificial hairs. However, she should — by obligatory caution — cover them in front of a non-maḥram, whether she is praying or not.

A Man's Praying with a Gold Ring
A man is not allowed to wear a gold ring at all, and the prayer he performs while wearing it is void as per obligatory caution.

White Gold for a Man
If it is gold that has been rendered white due to mixing it with another substance, wearing it is ḥarām for men. But, if it is platinum or if the gold-percentage in it is so low that it is not recognized as gold by the common view, there is no objection to it.

Men's Gold-plated Teeth
There is no problem for a man in having his teeth covered with gold or platinum. However, a problem arises in case of covering his front teeth with gold for the purpose of adornment.

'Conspicuous' Clothes
By obligatory caution, it is not permissible to wear 'conspicuous' clothes; yet, it is no problem to say prayer with it. By 'conspicuous' clothes, it is meant the clothes which is not suitable for the person due to its color, mode of tyloring, being worn out, etc. so that wearing them attracts people's attention and makes one conspicuous.