Error 500 "Internal Server Error".
Blogger Support has been diagnosing this problem, for a while, using a series of bX codes - and the codes thrown by this condition seem to change, from day to day.
The last time Blogger Support provided any description of the problem - or guidance how to solve the problem, they made general mention of "corrupt templates".
If you are unable to access the dashboard of your blog, and you see the mysterious "Error 500" - or if your readers report mysterious bX codes, when trying to load your blog - this may be part of your problem.
Changing the template is the most immediate way to resolve the problem at hand.
If you report in the forum, providing the URL of the blog, and we diagnose a corrupt template - the quickest way to get your blog back, online and maintainable, is to change the template.
Since the dashboard cannot be accessed, the best solution is to access the Template page directly, and bypass the menu.
- Logout, then login as the owner of the blog.
- Find the BlogID of the blog.
- Build the Template page access URL.
- Load the Template page, using the Template page access URL.
- Choose a new template - and get the blog online.
Logout, then login as the owner of the blog.
If you were using Draft Blogger, return to Live Blogger.
Next, logout from Blogger / Google, then clear cache, cookies and sessions, and restart the browser. Finally, log in to Blogger, using your administrator account.
Find the BlogID of the blog.
This is the simplest step, in the process.
If you are logged in to Blogger, as a blog administrator, in some cases, the "Design" link in the navbar will link directly to the Template page. If it does, continue with Step 5.
If you're lucky, you can just click on "Design" - and you will be at the Template page.
If your blog does not support "Design", the "New Post" link in the navbar will contain the BlogID.
That's from this blog.
Build the Template page access URL.
The Template page, for this blog, is accessed as
Substitute the BlogID for your blog, for "24069595".
Load the Template page, using the Template page access URL.
Click on the link (containing your BlogID).
Choose a new template - and get the blog online.
This part you're probably done, a couple times. Choose a template, from the selections on the Template page. I suggest that you start first with "Simple", just to get the blog online - and work forward, later.
Pick a new template. I suggest that you start with "Simple", just to get the blog online.
You can always pick another template, later.
After you pick a new blog template, reset the post template, then logout from Blogger / Google.
Finally, clear cache, cookies and sessions, and restart the browser. Then log in to Blogger again, and begin anew.
The bottom line.
Hopefully, you have a backup copy of the template, taken recently. You can use that in a separate test blog, and copy key recent tweaks. Or not. That's your choice. But the important task - getting the blog back online - is behind you.
And maybe for the next series of template tweaks, you might want to test more carefully, maybe using a test blog?
(Update 2016/02): It appears that Blogger Engineers are now diagnosing this problem, using a series of bX codes.