There are other parts of SEO which you should pay attention to after your audit to make sure you stay competitive. After all, the technical foundation isn't the end of the road for SEO success. It's important to pay attention to your competition's SEO activity, keep an eye on the newest search engine best practices, and maintain local SEO best practices if your business depends on customers visiting a physical address. All of these are elements of a successful SEO strategy and should be corollary to your audit and ongoing SEO maintenance.
If you link out to irrelevant sites, Google may ignore the page, too – but again, it depends on the site in question. Who you link to, or HOW you link to, REALLY DOES MATTER – I expect Google to use your linking practices as a potential means by which to classify your site. Affiliate sites, for example, don’t do well in Google these days without some good quality backlinks and higher quality pages.
QUOTE: “Some pages load with content created by the webmaster, but have an error message or are missing MC. Pages may lack MC for various reasons. Sometimes, the page is “broken” and the content does not load properly or at all. Sometimes, the content is no longer available and the page displays an error message with this information. Many websites have a few “broken” or non-functioning pages. This is normal, and those individual non-functioning or broken pages on an otherwise maintained site should be rated Low quality. This is true even if other pages on the website are overall High or Highest quality.” Google
You can confer some of your site's reputation to another site when your site links to it. Sometimes users can take advantage of this by adding links to their own site in your comment sections or message boards. Or sometimes you might mention a site in a negative way and don't want to confer any of your reputation upon it. For example, imagine that you're writing a blog post on the topic of comment spamming and you want to call out a site that recently comment spammed your blog. You want to warn others of the site, so you include the link to it in your content; however, you certainly don't want to give the site some of your reputation from your link. This would be a good time to use nofollow.
Another illicit practice is to place "doorway" pages loaded with keywords on the client's site somewhere. The SEO promises this will make the page more relevant for more queries. This is inherently false since individual pages are rarely relevant for a wide range of keywords. More insidious, however, is that these doorway pages often contain hidden links to the SEO's other clients as well. Such doorway pages drain away the link popularity of a site and route it to the SEO and its other clients, which may include sites with unsavory or illegal content.
The audit is for all pages and not only one. What happens in the majority of the cases is that pages / posts have similarities so you can group them together. For example the pages of a website may be ok but the blog post pages may be missing titles. It’s a lot of work especially for a 500 pages website but you can start from the most important pages first and work your way to the rest