function createRssFeedUrl() {
    var selectedCategories = document.getElementById('categories');
    var selectedUnlimited = document.getElementById('unlimited');
    var urlFeed = 'http://dbCF.de/WallpaperRSS/?';
    var outputUrlFeed = document.getElementById('urlFeed');

	if (selectedUnlimited.selectedIndex == 1) {
		urlFeed += 'unlimited=1';
	}

	var categories = '';
    for (var i=0; i<selectedCategories.options.length; i++) {
		if (selectedCategories.options[i].selected) {
			if (i == 0) {
				break;
			}
			else {
				categories += selectedCategories.options[i].value + ',';
			}
		}
    }
    if (categories != '') {
    	urlFeed += '&categories=' + categories.substring(0, categories.length - 1);
    }

    // Clean up url
    if (urlFeed.substr(urlFeed.length - 1) == '?') {
        urlFeed = urlFeed.substring(0, urlFeed.length - 1);
    }

    urlFeed = urlFeed.replace(/\?&/, '?');

	outputUrlFeed.href = urlFeed;
	outputUrlFeed.innerHTML = urlFeed;
}

createRssFeedUrl();