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?

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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.