How to check for 404 & 500 internal links on a given website ?
==============================================================

Have a look on the code below::

    /**
     * This casper script checks for 404 internal links for a given root url.
     *
     * Usage:
     *
     *     $ casperjs 404checker.js http://mysite.tld/
     *     $ casperjs 404checker.js http://mysite.tld/ --max-depth=42
     */
     
    /*global URI*/
     
    var casper = require("casper").create({
        pageSettings: {
            loadImages: false,
            loadPlugins: false
        }
    });
    var checked = [];
    var currentLink = 0;
    var fs = require('fs');
    var upTo = ~~casper.cli.get('max-depth') || 100;
    var url = casper.cli.get(0);
    var baseUrl = url;
    var links = [url];
    var utils = require('utils');
    var f = utils.format;
     
    function absPath(url, base) {
        return new URI(url).resolve(new URI(base)).toString();
    }
     
    // Clean links
    function cleanLinks(urls, base) {
        return utils.unique(urls).filter(function(url) {
            return url.indexOf(baseUrl) === 0 || !new RegExp('^(#|ftp|javascript|http)').test(url);
        }).map(function(url) {
            return absPath(url, base);
        }).filter(function(url) {
            return checked.indexOf(url) === -1;
        });
    }
     
    // Opens the page, perform tests and fetch next links
    function crawl(link) {
        this.start().then(function() {
            this.echo(link, 'COMMENT');
            this.open(link);
            checked.push(link);
        });
        this.then(function() {
            if (this.currentHTTPStatus === 404) {
                this.warn(link + ' is missing (HTTP 404)');
            } else if (this.currentHTTPStatus === 500) {
                this.warn(link + ' is broken (HTTP 500)');
            } else {
                this.echo(link + f(' is okay (HTTP %s)', this.currentHTTPStatus));
            }
        });
        this.then(function() {
            var newLinks = searchLinks.call(this);
            links = links.concat(newLinks).filter(function(url) {
                return checked.indexOf(url) === -1;
            });
            this.echo(newLinks.length + " new links found on " + link);
        });
    }
     
    // Fetch all <a> elements from the page and return
    // the ones which contains a href starting with 'http://'
    function searchLinks() {
        return cleanLinks(this.evaluate(function _fetchInternalLinks() {
            return [].map.call(__utils__.findAll('a[href]'), function(node) {
                return node.getAttribute('href');
            });
        }), this.getCurrentUrl());
    }
     
    // As long as it has a next link, and is under the maximum limit, will keep running
    function check() {
        if (links[currentLink] && currentLink < upTo) {
            crawl.call(this, links[currentLink]);
            currentLink++;
            this.run(check);
        } else {
            this.echo("All done, " + checked.length + " links checked.");
            this.exit();
        }
    }
     
    if (!url) {
        casper.warn('No url passed, aborting.').exit();
    }
     
    casper.start('https://js-uri.googlecode.com/svn/trunk/lib/URI.js', function() {
        var scriptCode = this.getPageContent() + '; return URI;';
        window.URI = new Function(scriptCode)();
        if (typeof window.URI === "function") {
            this.echo('URI.js loaded');
        } else {
            this.warn('Could not setup URI.js').exit();
        }
    });
     
    casper.run(process);
     
    function process() {
        casper.start().then(function() {
            this.echo("Starting");
        }).run(check);
    }