solved problem:
input labels, requires a transparent background, Google can use rgba, but need to be compatible IE8, rgba not supported on IE8.
When you think about how rgba transparent IE8 compatible, and will not think of another angle, is not directly remove the default background color.
Definition and Usage
background-color attribute set the background color element.
Range of background elements
background-color attribute set to a solid color element. This content will color fill element, padding and border region, the border element to the extended outer boundary (but not including margins). If the frame has a transparent portion (e.g., dashed border), the background color will show through the transparent portion.
transparent value
Although in most cases, there is no need to use transparent. But if you do not want to have the background color of an element, but do not want the user to set the color effect on the browser to your design, then set the value of the transparent or necessary.
Unusual, two values need to make notes, record it.
I hope I can help you.
by without saying thanks