Try these two changes:
Remove the single quotation marks around the $start_row , 10 term and remove the semicolon inside the double quote marks. So that your statement looks like this:
$result=mysql_query("SELECT markaid, MarkName, modelid, ModelName,
ModelPic, telinfo, cena, grad, kontakti, date FROM sell
ORDER BY date DESC LIMIT $start_row, 10 ");
You might be able to (single)-quote the $start_row and 10 terms separately, but I'm not sure how SQL handles quoted numeric terms.