NOTE: This script will prevent just text selection on blog. To completely remove copy paste option you will have to disable right click also.
To disable right click : Click Here
<!- start disable copy paste --><script src='demo-to-prevent-copy-paste-on-blogger_files/googleapis.js'></script><script type='text/javascript'> if(typeof document.onselectstart!="undefined" ) {document.onselectstart=new Function ("return false" ); } else{document.onmousedown=new Function ("return false" );document.onmouseup=new Function ("return false"); } </script>
<!-- End disable copy paste --></!->
To disable right click : Click Here