The shortest demonstration of dragging object code_javascript skills

This is the simplest code for dragging objects that I have ever seen on the Internet. I forgot the name of the author.
The original code has some minor problems under IE, and after declaring the document type as xhtml 1.0, it is invalid under non-IE browsers such as FF. It has been improved and is now compatible with: IE, Firefox, Opera... .
The following code is just a demonstration principle. Please modify it based on your actual needs for specific applications.