Add  Canvassing and Learn CSS Layout the pedantic way to HTML & CSS section.

According to Prof. Papadimitriou, the pdf we were linking to (as well as others on the internet) are not authorized by the current copyright owner, McGraw Hill.

Added:

Basic Algebra, Digital Second Edition (Anthony W. Knapp)
Advanced Algebra, Digital Second Edition (Anthony W. Knapp)

A book about an Nginx-based web development platform called OpenResty.

Removed the following link:
* [Python Algorithms](http://kysmykseka.net/koti/wizardry/Programming/Python/Apress%20-%20Python%20Algorithms%20Mastering%20Basic%20Algorithms%20in%20the%20Python%20Language.pdf) (PDF)

Ian Parberry, the author, requests that links point to a license page
leading to his books rather than directly to pdf. See
https://github.com/vhf/free-programming-books/issues/1769#issuecomment-1
70046046

The old one on SourceForge is not used anymore.

This fixes some 404s by removing them or changing the link if it's moved to a new location or avaliable elsewhere

Fix link to *Learning Modern 3D Graphics Programming*.  The source of the updated link is the author's [Wiki](https://bitbucket.org/alfonse/gltut/wiki/Home) for the book.