Question

My current link results in a 404 which is correct behavior.

Now the server gives back html code which i want to use as a page instead.

$(document).bind('pageloadfailed', function(e, data) {
    // use html from 404 result as var page that should be displayed now
    data.deferred.reject(data.absUrl, data.options, page);
    return false;
});

Answer 1

From XMLHttpRequest help page on W3C and by checking jQuery Mobile code, I would say it should be possible to get this way:

$(document).bind('pageloadfailed', function(e, data) {
    // use html from 404 result as var page that should be displayed now
    var htmlSource = data.xhr.responseText; // this should contain your page source
    data.deferred.reject(data.absUrl, data.options, page);
    return false;
});