<style>div {width 50px;}</style>

$('div').css({"width":"100px"});

function getOriginalCSS(target,styles){
    var output = {}
    for(var style in styles){
        var current = target.css(style)
        target.css(style,'')
        output[style] = target.css(style)
        target.css(style,current)
    }
    return output
}