Custom widget area issue

I have created a custom widget area in order to place my language switcher
in the header section of my website. The item appears in the correct position but before the page fully loads, it appears “broken”, like it is not styled. I imagine I have made some error in my code and I validated it but I can’t seem to understand where the error is.

This is my website:
http://www.opensolution.gr

this is the validation:
http://validator.w3.org/check?uri=opensolution.gr&charset=%28detect+automatically%29&doctype=Inline&group=0

Any suggestions are appreciated.