gistfile1.js

// jQuery.support.(displayTable|displayTableCell|margin0auto|positionFixed)

// jQuery.support.displayTable and displayTableCell - 
// to determine browser support for setting elements to that css display value

$.each(['','-cell'],function(k,v){
    $.support['displayTable'+v.replace('-c','C')] = (function(){ 
        var elem = $('<div>',{
            css : {
                display:    'table'+v,
                position:   'absolute',
                visibility: 'hidden'
            }
        }).appendTo(document.body || document.documentElement),
            support = ('table'+v) === elem.css('display');
            elem.remove(); 
            return support; 
    })();
})

// jQuery.support.margin0auto
// to verify that '0 auto' will center things. (ie6 should fail..)
$.support.margin0auto = (function(){ 
    var elem = $('<div style="width: 10px; position: relative; "><div style="margin-top: 0px; margin-right: auto; margin-bottom: 0px; margin-left: auto; width: 2px; "></div></div>')
            .appendTo(document.body || document.documentElement),
        support = elem.children()[0].offsetLeft === 4;
        
    elem.remove(); 
    return support; 
})();

// jQuery.support.positionFixed
// does the browser support `position:fixed`
$.support.positionFixed = (function(){ 
    var elem = $('<div>',{
            css : {
                position:   'fixed',
                top:        '42px',
                visibility: 'hidden'
            }
        }).appendTo(document.body || document.documentElement),
        
        // also account for page scroll
        support = parseInt(elem.offset().top,10) - (document.body ? document.body.scrollTop : 0) === 42;
        
    elem.remove(); 
    return support; 
})();