Problems editing main index.php page

Thanks Samboll for good info. However, yesterday I downloaded index.PHP from the theme which I am using but most of the errors indicated in Validator can not be changed on that page. So far I was only able to correct 3 – 4 errors.

I.e. When I click source info on bequiablog.com the page shows all the errors as indicated on the validator, but the downloaded page (index.php) has less script written on it. Many of the errors indicated such as below are not on that downloaded index.php page (some of the script is missing):

Error Line 46 column 10: document type does not allow element “center” here; missing one of “object”, “applet”, “map”, “iframe”, “button”, “ins”, “del” start-tag.

<p><center>www.bego

There must be another page which I have to download to make these corrections.