Share your experience!
Previously i use Xperia Acro S and there's no problem with this, but this Xperia Z, when using mobile network, i can't open certain web page, it says "404 NOT Found" (using Dolphin browser which runs Adobe Flash), but when i use WiFi network, it seems ok, same page can be open no problem at all. May i know why? Is it my service provider's issue or it's the setting with Xperia Z?
Now i found the mobile networking sometimes drop need to retry. WiFi no problem with this.
If you have another phone(make sure they use the same 3g/lte), try to see if you can access the same webpage using the same sim card. If still can't, then you need to report the issue with your cell provider.
However, if you can access the website on the other phone, try to isolate the problem.
- update you Internet Settings (Settings > Xperia > Internet Settings)
- try using different Network Mode (Settings > Mores... > Mobile networks >Network Mode)
- switch to different APN (Settings > Mores... > Mobile networks >Access Point Names)
good luck!
Thanks Zann, your options gave me an idea to solve it, i compare both new and old Sony phone and found differences at the APN settings, proxy and server set "Not Set" at the old Acro S phone and new phone there's numbers in it, so i delete both proxy and server to "Not Set" at new Xperia Z, problem solved! Those webpage can be open now. 
In the future, if proxy and server Not Set, will it makes any other difference or performance in the phone?