reloading webpage on safari downloads the page

I have a dynamic site I have made on PHP/MySQL and recently I have experienced a weird issue - sometimes 开发者_Python百科(about once in four times) when I reload the active page the safari web browser (on a mac) automatically downloads the xxxx.php page rather than reloading it! I am trying to figure out what could be causing this, but i have no idea. Any suggestions?

The Content-Disposition HTTP Header is the only thing I can figure. Is there any way you can post something that we can test?

could it be with the .htaccess? I had a similar problem last month and I had to change some entries in my .htaccess, the shared server may have changed Apache's settings and it sopped working properly.