import java.applet.Applet;

public class HelloApplet extends Applet {
java.awt.Label label = new java.awt.Label ();

private static final long serialVersionUID = 1L;

/**
* This is the default constructor
*/
public HelloApplet() {
super();
}

/**
* This method initializes this
*
* @return void
*/
public void init() {

try {
jbInit();
}catch(Exception e){
e.printStackTrace(); }
}
private void jbInit () throws Exception{

label.setFont("Dialog",Font.BLOG,25);
label.setText("欢迎学习JAVAAPPLET");
this.add(label);

}
}
帮忙修改下

import java.applet.Applet;
import java.awt.Font;

public class HelloApplet extends Applet {
java.awt.Label label = new java.awt.Label ();

private static final long serialVersionUID = 1L;

/**
* This is the default constructor
*/
public HelloApplet() {
super();
}

/**
* This method initializes this
*
* @return void
*/
public void init() {

try {
jbInit();
}catch(Exception e){
e.printStackTrace(); }
}
private void jbInit () throws Exception{

label.setFont(new Font("Dialog",Font.BOLD,25));
label.setText("欢迎学习JAVAAPPLET");
this.add(label);

}
}

别用awt了，用swing.

我按你的方法做了,怎么显示出来是　failed to load Main-Class mainfest attribute from D:\HelloApplet\HelloApplet.jar 错误呀？
能在详细说说吗？

你用什么运行的啊？？？
我用eclipse运行没问题啊
而且你是applet，怎么会有Main-Class???

不好意思发错地方了,你修改的是正确的