First of all thanks for sharing, it is what makes this place work!
Note - This is not a criticism, just a bit of awareness to those that might use the code.
In order for this to be minimally safe the field entries in the ACP should have a regular expression set for the user input and a field length. Otherwise I could simple add my own CSS to the template, or possibly something worse. Additional validity testing can also be added by using plugin/hook.
Again thanks for sharing.