The first, A Technical SEO Guide to Crawling, Indexing and Ranking introduced me to the concept of crawl budget, which is the amount of resources/time Google is going to spend crawling your site, and therefore determines how many pages get indexed.
Clearly, you don’t want Google to index lots of low value pages (for example, caused by navigation filters) and miss your higher value pages (such as your product pages or articles). There are a few ways to try and control this, such as rel=nofollow, which the article covers.
The second article is a Guide to Site Navigation for SEO. This article is useful because it looks at the implications of having too many navigation links on your site. For example, if your global drop-down navigation links to every category and sub-category on your site you could be reducing the amount of ‘link juice’ passed to lower level pages.
In addition, if you are using category page filters to make it easier for people to browse for products, you could be inadvertently creating thousands of low value pages, which both uses up your crawl budget and reduces the page authority being passed from these important category pages.
To improve how category navigation and filters work for the Magento store I manage, we installed the Improved Navigation extension from Amasty. It’s well worth checking out if you’re a Magento user.
Bonus article: if you regularly have to deal with stakeholders or clients who insist that calls-to-action must be above the fold, this article debunking the above the fold myth should help provide some evidence to the contrary.