1.HTML4 supports the ‘tag soup’ i.e. the ability to inscribe malformed code and get them accurately on the document. But there are no written rules or guidelines for doing this. This implies that malformed documents are to be tested on various browsers.
2.To tackle this issue, HTML5 is being developed in such a way so that the developers need not waste their time and efforts in creating an error free web page.
3.Unlike its predecessor, HTML5 also includes many new tags and also new names for older tags with extra features like: local storage wherein a lot of information can be stored, JS-based hacks or Flash, validation form etc. so as to make the applications easy for the developers and speedier for the users.