Defines the minimum width in percent of the containing block.
or using px means,
.container{
min-width:1200px;
width: auto !important; /* Firefox will set width as auto */
width:1200px; /* As IE ignores !important it will set width as 1000px; */
}
or see this stack overflow link.It may helpful.
StackOverFlow for all sizes of window
I have used like this in my site,
@media screen and (max-width:320px) { */Your styles*/}
@media screen and (min-width:321px) and (max-width:639px) {}
@media screen and (min-width:640px) and (max-width:959px) {}
@media screen and (min-width:960px) and (max-width:1279px) {}
@media screen and (min-width:1280px) and (max-width:1599px) {}
@media screen and (min-width:1600px) {}
@media screen and (min-width:1920px) {}