CSS Class Selector:
Class selector using (.) dot notation can be used to select elements that have a class attribute containing a specific value or values.The name of the class value must immediately follow the dot (.)
*.design { color: gray } OR .design { color: gray }
/* to set a color for all elements with "design" class */
p.design { color: gray }
/* to set a color for "p" elements with "design" class */
<p class="design">Web Design</p>
p.design.develop { color: gray }
/* to set a color for "p" elements with "design"
and white separated with develop class */
<p class="design develop">Web Designing & Development</p>CSS ID Selector:
ID selector using “hash notation” can be used to select elements that have an ID containing a specific value or values. The name of the ID value must immediately follow the octothorpe (#). An ID typed attribute can be used to uniquely identify its element. There is no two such attributes can have the same value in a conforming document.
*#testing { color: red } OR #testing { color: red }
/* to set a color for all elements with "testing" id */
p#testing { color: red }
/* to set a color for "p" elements with "testing" id */
<p id="testing">Web Testing</p>