CSS Buttons when viewed on windows desktop or apple mac have a default background color of grey (#DDD) but when viewed on ios mobile, the default background color is transparent. This can be fixed by manually adding css background color as #DDD but still why does this happen? Any Ideas?
They look different because browsers have different renderings of CSS.
I recommend to use -webkit and -moz to avoid this type of problem.
.btn{
-webkit-background-color: #DDD;
-moz-background-color: #DDD;
background-color: #DDD;
}