Misconception: Students frequently confuse the commenting syntax for HTML and CSS.

Like 
  • For example novices may try to comments using the following syntax:
    • / CSS comment
      • The correct syntax for a CSS comments is as follows:
        • /* Comment Goes Here */
    • // HTML comment
      • The correct syntax for HTML comments is as follows:
        • <!-- Comment Goes Here -->
  • This type of error is called a rules-based error. It occurs when the student is familiar with the basic rules and constructs of a language, but comes up against an unknown exception, edge case, rule, etc.
    • This may be the result of incorrect research or assumptions about what is valid, or it can simply be the result of not knowing all the rules, exceptions and edge cases for programming with HTML and CSS.
External Source: 

"Towards a Taxonomy of Errors in HTML and CSS" by Thomas Park, Ankur Saxena, Swathi Jagannath, Susan Wiedenbeck, and Andrea Forte.