Hi Guys,
I’m using OS 4.11 on x86, and very difficult to open only yahoo site, other sites with fast access, I changed my server to windows server and works fine, when I replaced it with Mikrotik OS the same problem occur. Way out pls 
Wild guess: http://wiki.mikrotik.com/wiki/Manual:RouterOS_FAQ#TCP.2FIP_Related_Questions
I cannot surf some sites when I use PPPoE.
Use /ip firewall mangle to change MSS (maximum segment size) 40 bytes less than your connection MTU. For example, if you have encrypted PPPoE link with MTU=1492, set the mangle rule as follows:/ ip firewall mangle
add chain=forward protocol=tcp tcp-flags=syn action=change-mss tcp-mss=!0-1448 new-mss=1448
Are you using PPPoE? It’s extremely unlikely that only Yahoo! loads slow/incompletely. Maybe it’s the only site you tested that did that.
Yes, yahoo is the only site difficult to open and I’m not usin PPPOE. OTHER SITES OPEN EASILY
so, did ‘change-mss’ rule help?
No positive changes yet!!! 
Hi Guys,
Fresh instalation of OS 4.11 took place, still yet the same promblem even after changing the mss rule. What bordering me now is : I can access yahoomail with only a secure ip site www.suresome.com or any alternative to change/hide ip address.
While accessing with my ip address it shows the follows:
Automatic page updates causing problems with your screen reader?
If you are using a screen reader and having problems using Mail, it might help to disable automatic page updates. Please note, this will also disable chat and text messaging within Yahoo! Mail. You can toggle automatic updates on and off using the link below. Disable automatic page updates.
Waiting for the way out.
Thanks