the purpose of using step attribute in input tag in html?
input type="number" name="points" min="0" max="100" step="10" value="30"
From the above line minimum length is zero, maximum length is 100, default value is 30 but i can't understand what action doing when assign step="10"
The step attribute specifies the legal number intervals for an element. Example: in your case, step="10", legal numbers could be -10, 0, 10, 20, etc. Still if you can't get it, you can go through this link.
http://www.w3schools.com/tags/tryit.asp?filename=tryhtml5_input_step