Every BlogSpot user Faces this Problem Mainly during changing Blog Template or sometimes During Deleting a Particular Widget. These codes are created by the Blogger system when an error occurs to help the Blogger team track down and solve any problems.
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I read an article which said : The code refers to a JSON-callback to the Blogger Error Codes blog. This is used a "database" of error codes which is used to display a message if the specific error code has been registered on this blog.

The Blogger Error Codes blog uses posts organized by labels attributed to a particular error code. When a particular error occurs, the error page references the bX-codes blog. If this matches an existing label, the body of the post attributed to this label is used to display a message to the user to inform them of the problem or explain that the Blogger team are aware of the problem.

How to Solve the Problem Hack It Up’s Way ?

Step 1 : Close the Browser Window & Clear the cookies and cache – Doing This Solves all the Problem of the bx Problem.

Step 2 : Another way ( only when you are changing Templates ) – Sometimes if there are a Lot of HTML widgets that are shown to be deleted, then Go Back to Layout > Page Templates and delete all the HTML Widgets. Now go to Edit Template to Update your Template. Even if the Problem persists Follow Step 1.