$(document).ready(function(){
  $("td").hover(function(){
        this.focus();
    if(window.getSelection){
        var range=document.createRange();
        range.selectNodeContents(this);
        var selection = window.getSelection();
        selection.removeAllRanges();
        selection.addRange(range)            
        }
    else if(document.selection){
        //for ie
        var range=document.body.createTextRange()
        range.moveToElementText(this)
        range.select();
    }
  },function(){
  if(window.getSelection){
        var range=document.createRange();
        range.selectNodeContents(this);
        var selection = window.getSelection();
        selection.removeAllRanges();
         
        }
    else if(document.selection){
        //for ie
        var range=document.body.createTextRange()
        range.moveToElementText(none)
        
    }
  });
});

选中？还是说鼠标经过改变样式（hover css属性）