But there is no "real-life" or practical benefits of replacing <table> tag with <DIV>
There is, ( for starters you have replaced the SEMANTICALLY incorrect TABLE tag for non tabular data) , still it does waste the potential for a having actually well coded design.
Can i work on css in graphic user interface format like tables.
one can do anything if one knows how.
THE IMPORTANT THING TO KNOW, is that CSS helps you SEPARATE content from layout ( what I assumed you mean by " graphic user interface format". If you are still trying to make the page content dependent on it's layout then you will get it wrong even if using DIVs.
Create a WELL STRUCTURED HTML document FIRST. Then use CSS to style/display the content as desired.