The purpose of starting an initial comment with /*! in javascript and css files
Solution 1:
It tells compression tools such as the YUICompressor and Uglify, which minify the code, to leave the commented section in place as they usually remove all comments from the code.
Solution 2:
I believe one purpose of the exclamation point is to tell javascript minifiers to leave these particular comments in, when condensing the files.
Solution 3:
Some software like Coda also support the "bookmark syntax" shown below, so that one can navigate to different parts of code through the app's code navigator.
// !bookmark
/* !bookmark */
<!-- !bookmark -->
Note that in the examples above there's a space between the comment syntax the exclamation mark.