media query for 320px and less

[m4rc310]

I am writing a media query for a web-page and managed to write media queries for 480px and more. But when I write media query for 320px it doesn't work properly. I want to capture the portrait views of most of the mobiles( iphone4, iphone5,iphone3,asus galaxy 7,samsung galaxy sII, samsung galaxy s3 ) which is 320px. The webpage I created was working with landscape views in these devices but doesnt scale for portrait views. Can anybody please point out the error in the query. This is the media queries I used.\[code\]@media (max-width: 320px){ html { font-size:0.1em; }}@media (max-width: 480px){ html { font-size:0.20em; }}@media (max-width: 767px){ html { font-size:0.38em; }}@media (min-width: 768px) and (max-width: 979px) { html { font-size:0.65em; } } @media (min-width : 980px) and (max-width:1025px) { html { font-size:0.7em; } }\[/code\]For 320px I also tried with \[code\]@media only screen and (min-device-width : 320px) and (max-device-width : 480px) and (orientation : portrait){ /*Styles */}\[/code\]and \[code\]@media only screen and (max-width : 320px) {/* Styles */}\[/code\]But none of them is working.Am I doing anything wrong/missing something?Thanks in advance