Get css top value as number not as string?

A jQuery plugin based on M4N's answer

jQuery.fn.cssNumber = function(prop){
    var v = parseInt(this.css(prop),10);
    return isNaN(v) ? 0 : v;
};

So then you just use this method to get number values

$("#logo").cssNumber("top")

You can use the parseInt() function to convert the string to a number, e.g:

parseInt($('#elem').css('top'));

Update: (as suggested by Ben): You should give the radix too:

parseInt($('#elem').css('top'), 10);

Forces it to be parsed as a decimal number, otherwise strings beginning with '0' might be parsed as an octal number (might depend on the browser used).