animation in applet

Hello sir,
your code is ok
but what happend to this code can you modify this an tell me problem please
code:


import java.applet.*;
import java.awt.*;
import java.net.*;
/*<applet code="Moveplane.class" height=600 width=800>
</applet>
*/
public class Moveplane extends Applet
{
public void paint(Graphics g)
{
Font f=new Font("Arial",Font.BOLD,30);
g.setFont(f);
g.setColor(Color.green);
g.drawString("Telangana AirLines",300,35);

try
{
Image i1=getImage(getDocumentBase(),"a1.gif");
g.drawImage(i1,50,50,null);

Thread.sleep(100);
}
catch(Exception e){}
for(int s1=7,s2=70; s1<6100||s2<3000;)
{

if(s1<610)
s1=s1+9;
if(s2<300)
s2=s1+20;
try
{
Thread.sleep(100);
}
catch(Exception e){}

}
}
}