Go to the auxiliary blog and post your comment there. If you're commenting on a particular article, PLEASE include the title or URL of the article so I can find it. Also, if you're asking about a particular equation in a post, PLEASE include the equation number. Many of these posts were written several years ago so they will not be fresh in my memory.
If a comment asked for an explanation of something, I will add my response to the comments at the end of the relevant post. If you can't see the response, it may be because your browser is using an old cached version of the page. Try clearing your browsing history for the past few hours or days. The method for clearing browsing history varies with the browser, but for Google Chrome, click on the icon with three vertical dots in the upper right corner, select "More tools", then "Clear browsing data". Then click "Cached images and files" (and make sure no other checkboxes are selected unless you want other stuff to be cleared as well), and select the time interval from the drop down menu at the top.
I'm working through some textbooks at my own pace and according to my own interests, so sadly, no, I can't accept requests to post articles on specific problems or textbooks. (Also, my own knowledge is quite limited, so I don't know the answers to everything!) If you want help with a particular problem, you can try joining Physics Forums or Physics Stack Exchange where a large audience is available to help you with physics-related problems. Note that to get help there, you will need to show that you have made a serious attempt at solving the problem yourself before asking for help.
I will post a link to each new article on the auxiliary blog and you can sign up for email notifications for that blog.
The current version of physicspages.com was created in October 2017, and is a completely rebuilt version of the original site which dates from 2011. As such, the URLs of all the pages have been changed since the earlier version, so Google may still have some of the older URLs in its search database. Hopefully, these old dead links will disappear over time.
No, since I periodically update files with corrections or additions, and also pingback links are added to older posts that link them to later posts. If I provided a single PDF with all the existing posts, I'd have to update this file every time any of the files within it were modified, which isn't practical.
The short answer is NO! I, like most other internet users, find ads highly annoying, so I will not clutter up physicspages with them. The site is entirely non-profit and will remain so. If you represent a company that wants to place ads on physicspages, please don't waste my time (or yours) by asking.
I write the posts entirely in Latex using the Lyx editor, which is free. It requires an installation of Latex on the same machine, but this is provided as part of the Lyx download.
To handle lengthy or tedious calculations and to draw plots I use Maple. Maple isn't free, but there is a personal edition available for a much reduced price. To get this, you need to convince them that you're not associated with a university or business, and that you aren't making any money out of it. For me, this was just a matter of exchanging emails with them explaining I was using Maple for a non-profit physics blog. The Maple personal edition is identical to the full version, so it's not missing any features. If you plan to do a lot of calculations, I find the investment is well worth it. If you're on a limited (or zero) budget, there is a free mathematics package called Maxima which I've heard is quite powerful, though I've never used it.
For Feynman diagrams, I use JaxoDraw, which is also free. To produce Latex text within the diagrams, you do need to have Latex installed separately.
For other types of diagrams, I use the Draw program which is part of the LibreOffice package, which is also free. For general editing of HTML files, I use Notepad++, which again is free.
A bit of info about me is available on my personal web site, although I don't maintain it very often.