Both text-align: and margin-left will affect the complete text block. They won't be the source of the indent.
You may have a text-indent: (
http://www.w3schools.com/css/pr_text_text-indent.asp ) value set in a style, either in the HEAD section or in a CSS style sheet. If you find one, set it to zero.
Also, since the Kindle device is the single largest market for MOBI format ebooks I suggest that you download a copy of Kindle Previewer for proofing. Kindle for PC is not a good match to the Kindle device display. The Kindle Previewer is written specifically for proofing; it is a very good match. You can get it here:
http://www.amazon.com/gp/feature.htm...cId=1000234621