Cross-browser CSS3 transition parse errors

I've set cross-browser css3 bg transition

background: #999; /* for non-css3 browsers */
filter: progid:DXImageTransform.Microsoft.gradient(startColorstr='#fff', endColorstr='#dadada'); /* f开发者_如何学Pythonor IE */
background: -webkit-gradient(linear, left top, left bottom, from(#fff), to(#dadada)); /* for webkit browsers */
background: -moz-linear-gradient(top,  #ccc,  #000); /* for firefox 3.6+ */ 

But when i'm opening this page for example on Firefox it give me parse errors

Error in parsing value for 'background'. Declaration dropped. @ styles.css:43

Error in parsing value for 'filter'. Declaration dropped. @ styles.css:43

How can i prevent it?

You can't stop those parse errors. Firefox doesn't understand the filter property and from Firefox's perspective, that webkit syntax is wrong. That's what happens when standards aren't finalized yet.