For girls, it's usually an accident. We are almost never aware of how guys view things. Like when girls were mini skirts, guys will assume, "Oh, she wants to show off some leg and attract guys' attention." But that isn't the case I'd say 87% of the time. We just think the skirt is cute and stylish! Girls DO NOT realize how little peeks of skin/bra/underwear affect guys. Although, if a girl has 70% of her thong peeking out, that's definitely an attention hoe. There's always that 13% that crave male attention. For the most part, girls are clueless.
if i see it like on accident like while she's siting or bending over.. it turns me on soo much.. call me a pervert or what ever... i love it when her underwear is the kind with the brand name written on the waistband. also on the same subject i like to see panty lines.. i always try and guess what kind she is wearing by the outline.