Page Not Found Error While Trying To Edit And Save ?

Arvind,

Q: I have a problem where every time
I edit a post, 1 out of 2 times when
I save it, I get the message that
the page is not found!

This is strange and most annoying, if you had written a lengthy article and lost due to such weird behavior! If you encounter such a situation, then hit the back button on your browser and most of the time(if you are using Chrome and Firefox) your data will be safe. Thanks to browser cache.

Normal Reason For This Problem
The reason for such problem maybe the URL slug. Never have those weird characters in the URL slug. If you have double quotes or single quote or some special characters in the Title, make sure you remove those characters special code from the URL slug. Because some browsers may interpret these characters differently, hence behave in different manner.

The “slug” is the URL-friendly version of the name. It is usually all lowercase and contains only letters, numbers, and hyphens

SEO Wise
Best practice is to remove unwanted words and characters from your URL slug.
Ex: My Title is “Page Is Not Found Error While Trying To Edit And Save ?”

Here remove My, Is, While, To, And etc and retain only the main keywords which you think are most relevant to the article.
So my article’s URL looks : http://technotip.org/page-not-found-error-edit-save/
My title is still Page Not Found Error When Trying To Edit And Save ?

More sophisticated problem
If you don’t have any special characters in your URL slug and still have this problem, then your next suspect should be plugins.
Deactivate one plugin at a time and try to edit and save. By repeatedly doing this trial and error method you can detect what plugin might be in conflict.

Also make sure you have all latest plugins and have upgraded your WordPress installation to the latest version. Most of the times these bugs will be fixed, but we forget to update the software and face the consequences!