How to style a div to have a background color for the entire width of the content, and not just for the width of the display?

Question

I have an HTML page that for the sake of this question looks like this:

                  
        
        

          

            
            

              
              

            
    


                                 
              
            
                          
    

        
         

                验证码
                

                  
                
                

                   看不清?
                
              
                                  

                    
   
                 
             
              
提交回复