Yesterday I have discovered, that on some pages AdSense advertising does not show under IE 6.0, also on these pages IE informed on an error:
Строка: 2 РЎРёРјРІРѕР»: 1 РћС?РёР±РєР°: Недопустимый знак РљРѕРґ: 0
Yes, the error message in Russian, and may be translated as "Illegal symbol" at line 2 character 1. All these pages have had <head> at this place long time ago, and IE have had no problem with these pages. Perhaps, recent automatic updates from Microsoft may cause this strange behaviour.
Today I found out what IE doesn't like. All those pages have had the following DOCTYPE:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
For example, this DOCTYPE is inserting automatically when xemacs creates a new html page.
After I have changed DOCTYPE to one recomended by W3C:
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
"http://www.w3.org/TR/html4/loose.dtd">
IE is happy now with these pages, the error message has gone away and AdSense advertising shows again.