This is the question I ask when I attempt to leave my house wearing something not at all pleasing to my parents. Of course I’m not wearing anything bad, they just have a different definition of "appropriate".
Now I have been taught that I’m not allowed to wear anything too short and too low so I try my best to stick to modest dress. I still at times fall short of the mark, because like I said my parents have different standards. God has standards also and in the Bible God refers to our bodies as His temple. We’re supposed to respect ourselves with what we wear. When I dress inappropriately, I’m not only disrespecting myself, but also those around me.
I recently finished reading "I Kissed Dating Goodbye" with a group of friends my age. One of the chapters went into detail about how distracting it is for boys when we girls walk around wearing really short shorts or very low cut tops. We are supposed to respect our brothers in Christ not lead them into temptation. One of the chapters asked the boys what they thought about girls who dressed immodestly. Most of the boys confirmed their appreciation when girls respected them enough to dress modestly.
So as I conclude, you might not find it a big deal. But I tell you it is to my parents and more importantly, it is to the Lord. We should all keep that in mind. And I guess my parents and I are getting closer to reconciliation on the definition of "appropriate". But just in case, say a prayer for me.