（答え）

1.
//送信データの作成
String sendData = "browser=" + URLEncoder.encode(browser) +
"&referrer=" + URLEncoder.encode(referrer) +
"&compname=" + URLEncoder.encode(compName);
↓書き直す
String sendData = "browser=" + URLEncoder.encode(browser,"UTF-8") +
"&referrer=" + URLEncoder.encode(referrer,"UTF-8") +
"&compname=" + URLEncoder.encode(compName,"UTF-8");

2.
C:\Documents and Settings\Owner>set path=c:\j2sdk1.4.0_02\bin;%PATH%

3.
C:\Documents and Settings\Owner>cd c:\j2sdk1.4.0_02

4.
C:\j2sdk1.4.0_02>javac GetIpApplet.java

入力に自信がない場合、すべての作業をコピペでおこなうこと。