Use HTML tag names, classes or IDs in CSS?

Question

In designing the HTML and CSS for a page, when should I use

img.className

versus

.clas

Answer 1

Yes. You may want to use the same classname for two elements in the future. Be explicit and clear. This will also prevent class-rules from overlapping onto unintended elements.

h1.title { font-size:18px; } /* My h1's are big */
 p.title { font-size:16px; } /* My p's are smaller */

  .title { color:#336699; }  /* All titles are blue */

Use ID's only when necessary, and only once per page.