Blank row before doctype

I am facing a strange problem. One blank row is coming in browser before doctype statement. I though it might be some php echo/print/print_r of some variable or a carriage return. I search the source code but no such thing found.Then I set a echo which is printed on 1st line i.e. on blank row. I look into header tpl file and add some string before doctype and found that its displaying on 2nd line with doctype, still 1st line blank. If I omit the css then also that blank row comes but no effect of it can be found in display with IE/MOZILLA . It can be found in source code only and the problem is for rss feed its creating following error :

“XML Parsing Error: XML or text declaration not at start of entity”.

If I save the xml in a file and execute it in browser then its working properly i.e no problem in xml value/format.

Any help is appreciated.

There was extra space in one of the module files which was creating that problem.

Thanks for the feed back!