use jquery to test for changed css property and make responsive changes. instead of checking on browser width

example.css

//The CSS
.tocheck {float:left;}
@media only screen and (max-width: 800px){
	.tocheck {float:none;}
}

example.js

//The jQuery
$(document).ready(function() {
    // run test on initial page load
    checkSize();

    // run test on resize of the window
    $(window).resize(checkSize);
});

//Function to the css rule
function checkSize(){
    if ($(".tocheck").css("float") == "none" ){
        // your code here
    }
}