Enter key doesn't work in firefox and chrome but working in IE

Hi, Experts

http://1-800-optisource.com/search.aspx?keyword=
i have two user control one is quick search and other one is advanced search
so quick search control in main master page and the advanced search is in mainmaster.searchmaster
so when click on the quick search is auto redirect to advanced search and display the product  after open that page and when i will write something on keyword textbox and hit enter key from keyboard it's searching the IE but it's not working in chorme or FireFox

i tired
this.page.form.defaultbutton = btnsearch.uniqueID

and i also give the asp panel default button

but still not working


Please help me

Thanks