<FORM name="form1">
<INPUT TYPE="text" NAME="txt1"><INPUT TYPE="button" onclick="check(txt1.value);">
</FORM>
<SCRIPT LANGUAGE="JavaScript">
function check(str){
var part=/^http:\/\/\w+\.{1}\w+\.{1}\w+/g;
if(part.test(str)){
alert("url合法");
}else{alert("url非法")}
}
</SCRIPT>