Please teach me how to use Baidu free code_html/css_WEB-ITnose

Baidu free code

<SCRIPT language=javascript>function g(formname)	{var url = "http://www.baidu.com/baidu";if (formname.s[1].checked) {	formname.ct.value = "2097152";}else {	formname.ct.value = "0";}formname.action = url;return true;}</SCRIPT><form name="f1" onsubmit="return g(this)"><table bgcolor="#FFFFFF" style="font-size:9pt;"><tr height="60"><td valign="top"><img src="http://img.baidu.com/img/logo-137px.gif" border="0" alt="baidu"></td><td><input name=word size="30" maxlength="100"><input type="submit" value="百度搜索"><br><input name=tn type=hidden value="bds"><input name=cl type=hidden value="3"><input name=ct type=hidden><input name=si type=hidden value="www.baidu.com"><input name=s type=radio> 互联网<input name=s type=radio checked> www.baidu.com</td></tr></table></form>                                    

This is a free code found on Baidu’s official website. I want to understand the meaning of the code and expand its functions myself.
For example: Implement multiple radio buttons to search on different websites.

I can basically understand the html code, but I don’t know the use of some tn, cl, ct, and js? I hope experienced experts can give me guidance.

Reply to discussion (solution)

Do you want code comments?

function g(formname)    {var url = "http://www.baidu.com/baidu";//设个默认变量urlif (formname.s[1].checked) {//查找formname里面第二个name为s的input是不是被选中    formname.ct.value = "2097152";//如果是formmname里面name为ct的input的值设为2097152}else {    formname.ct.value = "0";//没选中的话设为0}formname.action = url;//formname的action(就是提交地址)指向urlreturn true;}

<form name="f1" onsubmit="return g(this)">

When the above form is submitted, it will call the g method and pass itself in as a parameter (that is, the formname in the g method).