If you want it to hide at 729px exactly you could try using width
instead of max-width
.
If you want it to hide from 729px and above(which would guess you'd want) it might be better to tell the CSS to start hiding above 729px, and not below, as you are doing now.
If you change
@media only screen and (max-width : 729px) {
to
@media only screen and (min-width : 729px) {
it should work.
As Marcel W, said you could leave the only
part away. It makes small difference for newer browser, but it makes a big difference in older browsers.
The only
part gets ignored by older user agents as they don't reconize the property, thus letting you hide that part of the stylesheet from them. A newer user agent just ignores it and continues with the rest of the media query. Meaning that it is up to you to decide if you will or won't use it. If you want more info over only
check this link