Please let me know about these warnings

sir /madam

I have validated css for the following url with css level 3 but still showin 5 warning while no error in my code.

I have found 5 and some times while refreshing (3 or 8) wranings are occuring.

http://concepts2.sitesinprogress.co.uk/template10/css/master.css

549 #leftnav li a.heading You have no color set (or color is set to transparent) but you have set a background-color. Make sure that cascading of colors keeps the text reasonably legible.

 549 #leftcol h2 You have no color set (or color is set to transparent) but you have set a background-color. Make sure that cascading of colors keeps the text reasonably legible.

 549 #topnav li a You have no color set (or color is set to transparent) but you have set a background-color. Make sure that cascading of colors keeps the text reasonably legible. 

549 #callmeback input.three You have no color set (or color is set to transparent) but you have set a background-color. Make sure that cascading of colors keeps the text reasonably legible.

 549 .latestNews h2 You have no color set (or color is set to transparent) but you have set a background-color. Make sure that cascading of colors keeps the text reasonably legible.

Can you please check and reply me where I am missing the things for these warnings or it is compiler/validator's error?

Regards:
a Validator