Restricting HTML or Javascript tags in input

following is javascript to restrict HTML or javascript tags in input.

function RestrictTags()
{
txt_box=document.getElementsByTagName('INPUT');
for (txt_0=0; txt_0 < type="="'text')" str1="parseInt(txt_box[txt_0].value.indexOf('<'))" str2="parseInt(txt_box[txt_0].value.indexOf('">'))
if (str1 >= 0 || str2 >= 0 )
{
alert("HTML or JavaScript tags are not allowed");
txt_box[txt_0].value='';
txt_box[txt_0].focus();
return false;
}
}
return true;
}