css standard screen size

Browsing the web, I found the following sizes which can be used for standard screen sizes:

/* Smartphones (portrait and landscape) ----------- */
@media only screen  and (min-device-width : 320px)  and (max-device-width : 480px) {
/* Styles */
}
/* Smartphones (landscape) ----------- */ 
@media only screen  and (min-width : 321px) {
/* Styles */ 
}  
/** Elements */  
/* Default sizes */  
/* Smartphones (portrait) ----------- */ 
@media only screen  and (max-width : 320px) { 
/* Styles */ 
}  
/* iPads (portrait and landscape) ----------- */ 
@media only screen  and (min-device-width : 768px)  and (max-device-width : 1024px) { 
/* Styles */ 
}  
/* iPads (landscape) ----------- */ 
@media only screen  and (min-device-width : 768px)  and (max-device-width : 1024px)  and (orientation : landscape) { 
/* Styles */ 
}  
/* iPads (portrait) ----------- */ 
@media only screen  and (min-device-width : 768px)  and (max-device-width : 1024px)  and (orientation : portrait) { 
/* Styles */ 
}  
/* Desktops and laptops ----------- */ 
@media only screen  and (min-width : 1224px) { 
/* Styles */ 
}  
/* Large screens ----------- */ 
@media only screen  and (min-width : 1824px) { 
/* Styles */ 
}  
/* iPhone 4 ----------- */ 
@media only screen and (-webkit-min-device-pixel-ratio : 1.5), only screen and (min-device-pixel-ratio : 1.5) { 
/* Styles */ 
}

Sources: