In the latter case, neither the content nor the sidebar is actually missing. One or the other has simply slipped to the bottom of the page. Of course, it never occurs to somebody to scroll to the bottom in search of the missing content or sidebar. Why should it? It's called a sidebar because it's a BAR (column) that sits at the top of the page, beSIDE the column with the content (Posts). DOHH.
(Update 2009/11): This month, people using the "Jump Break" feature in the new post editor are seeing a dropped posts or sidebar section. If you're trying that feature, aka "Read More", in your blog, that's probably why you're here now.
This is a well known problem, and most frequently afflicts Internet Explorer V6.x. When this is observed in IE V6.x, but not in other versions of IE, and / or not in Firefox or Opera, there are several known causes.
- Check float alignment. Look in your settings, under Formatting, at "Enable float alignment". Is it set to "Yes"? Change to "No", Save Settings, and Republish.
- Look in the template, at the sidebar code, for graphics, like the Blogger Power Button, that may be too wide for the sidebar. Move anything suspicious to the bottom of the page, save the template, and republish.
- Look more carefully in the template, at other entries in the sidebar. Look for entries with long links, or long titles. Shorten or delete any found, save the template, and republish.
- Compare a view of the main page, with views of the individual posts.
- If you see the problem in all views, the problem is likely in the sidebar or template.
- If you see even one post where the problem does NOT appear, the problem is, most likely, present in the multiple individual posts where the problem does appear. Note: In one extremely odd situation, the problem was in a post title, and became active when the post title appeared in the sidebar, in the Previous Posts list.
- If no solution is found yet, isolate the problem using structured diagnostic procedures.
(Edit 11/14): It's possible that you can add 4 CSS rules to your template, that will make IE behave like Firefox, and make the above diagnostics unnecessary. If you're feeling adventurous, try an alternative procedure.
This list is probably not all-inclusive, but it may get you started. And if you come up with another cause for this problem, let me know, and I will be glad to add it to this list. And I'll back link to your blog, if you like. This blog is for help. I'll help if you will. BS probably won't.
See Peter's blog for more advice on post / sidebar alignment issues.