Thanks for your assistance, rachelmcr! I hope this is not too much information, nor not pertinent to the problems.
"...Are you seeing this problem when you look at the mobile theme version of your site on your iPad, or when you look at the full site..."
My sister (we are many states apart geographically) is the one with the ipad, and she is the jannpollard.com who initially had posted her support forum question in this regard, working on her own site, while helping me with my site. She was on the mobile version for her ipad. In the interim, I added this to my issues, because I think they might be related.
"...Would you be willing to take a screenshot of what you see on your iPad?..."
She probably could have taken a screenshot for me to offer to you, but she already fixed her viewing issue on her ipad based upon subsequent response to her question.
The solution for her was to clear her ipad cache, which worked on her end. I doubt that ipad users know to do that occasionally, so I think I should include a prominently displayed notice for mobile users somewhere static on my site. I know that the technology changes daily for these mobile devices, and the general public will learn eventually, but there always is a period of time for the learning curve.
"... You mentioned that the sub-menu items were in the header menu but not in your sidebar widget custom menu. Can you describe the steps you took to add the page to your sidebar widget custom menu?..."
No, that's reversed, and partial. What I said is that "....On an iPad, the top-most of the header sub-menu list for each "tab" is hidden from view .... That link is viewable from the sidebar widget custom menu, ..." (I know how fast you must be reading these: not to worry.)
All the sub-menu items appear - and function - just fine in the sidebar menu on computer, ipad, and Windows phone. [To answer your question, by the way, I added the sidebar "custom menu" as a widget, selecting the Menu same as the header menu.]
The header drop-down "hidden" (top-most) sub-menu items were made viewable after Jann cleared the cache on her ipad. I suspect, however, that the root of the problem may lie on the wordpress template side. (See * below.)
"...Can you give me a link to one of the pages that this happened with? (If this is currently happening with any pages on your site, you can also send a link to those. In that case, please don't fix the problem until I take a look — that can give me additional information.)..."
Your question relates to troubleshooting the Windows phone issue regarding sub-menu links from the header menu landing on a "page not found."
'Sorry: after subsequent experience, that might not have been the exact wording in the result; it could have been that there was no data for that page, which I just now discovered happening for one page accessed from my computer. (Yes, I now realize the importance of this detail... and how useful it might have been for me to take a screenshot of the result on my computer.) :(
On my computer there is the option to reload the page, which I did not get on my Windows phone mobile version, that I can recall. I'm 99% sure that on my phone I did go back one browser page and then come forward again, getting the same result.
The problem affected at least the following menu links, if I recall correctly, i.e. not all sub-menu links, and not all of the same parent files. I can find no function common denominator among them, since some are more complex pages, but others are not.
Ah-hah! I just realized - and it might help to know - that I tried these, BEGINNING with the top-most of the sub-menu list for each of the parents. I did not have the problem for the sub-menu items for which I started at the BOTTOM of the list for that parent page.
I'm sorry that I cannot recreate the problem on my phone. After I accessed those sub-menu pages by linking from the sidebar custom menu which appears at the bottom of the mobile version, the links from the header sub-menu all work just fine.
I tried to recreate the linking problem accessing pages from header sub-menus on my sister's site, but those links all worked just fine on my Windows phone, i.e. no problem. (I do not recall if I tried BEGINNING at the top of the list for the parent pages.) Thinking back, however, I might SINCE have downloaded a wordpress blogging app for my phone, which likely would "fix" things, relating to wordpress, in my browser. Only those Windows phone users who are site owners might download that app.
*The common denominators I can identify for these two issues are...
-1 both relate to mobile versions and not full versions;
-2 my sister and I both are using twenty-eleven theme;
-3 both issues relate to items of the header sub-menu, though one (ipad) seems to be a formatting problem based on the cache of the device, while the other (Windows phone) is a problem of linking to a page that fails to make a proper appearance... until after that page becomes cached in the phone;
-4 both issues MIGHT relate to the top-most item of the header sub-menu list for each parent menu "tab"; and
-5 (ah-hah! I just put this together) both issues relate to the cache.
Again, I hope this is useful to your efforts and not over-kill. Thank you for your help! -- Lucinda