Debug CSS error when generating pdf with TCPDF lib

Question

I have a problem where outputting a pdf with TCPDF. The CSS is not interpreted correctly. How to debug this problem ?

My HTML code :

                    
         
消灭零回复
 
                 
        
        

          

            
            

              
              

            
    


                                 
              
            
                          
    

        
         

                验证码
                

                  
                
                

                   看不清?
                
              
                                  

                    
   
                 
             
              
提交回复