Reduces N number of javascripts and CSS with the below cool attributes in HTML5

• placeholder :- lets you add a hint inside the textfield, but where the hint automatically disappears when you click inside it. 
• pattern :- lets you specify a regular expression (in JavaScript RegEx format) for legal values
• required :- it specifies that an input field must be filled out before submitting the form.
• autofocus :- element should automatically get focus when the page loads.
• list :- refers to a <datalist> element that contains pre-defined options for an <input> element.
• hidden :- it specifies that an element is not yet, or is no longer, relevant.
• contenteditable :- specifies whether the content of an element is editable or not.
• async :- can be used along with script. allows you to run the script asynchronously as soon as it is available

More details can be found in the below links

http://www.w3schools.com/html/html5_form_attributes.asp
http://www.w3schools.com/tags/att_global_hidden.asp