Can't access certain websites, flushdns solve the problem

Hi everyone,

After once Comcast and our IT vendor did something on the router, our Internet starts to act wired. Sometimes we can't access certain website, or it just shows only the text of webpage(no pictures, no styles).
Today, it happened to me again. I couln't ping the website. So I did some research, try to tracert the website, it looks fine. Then I tried flush dns, it solved the problem.
I just wonder what cause this problem and how can I solve it.

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What websites are you having trouble with.  I have found this issue with some bank websites and with cached dns records.  Also do you have a proxy or does your ISP have a proxy/cache server. I have found that these can cause issues also.  I have had to call one isp and have them exclude sites from their proxy/cache server.
zzl630Author Commented:
Website I have known with problems:

Sometimes I have problems with facebook and ebay too.
I don't think we have a proxy. Like I said it is just a two-three hours off, then it will back to normal.
zzl630Author Commented:
This is happening right now today.
Can't access

Ping request could not find host Please check the name and try agai

Server:  UnKnown

*** UnKnown can't find Server failed

Unable to resolve target system name

Tried flushdns, doesn't work.

Tried contact comcast. They said everything is fine.

Any suggestions?
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zzl630Author Commented:
Other websites seem working fine.
zzl630Author Commented:
DNS was setted up wrong.
Try to get the correct dsn from Comcase or use

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zzl630Author Commented:
Solved by my self , after searching on other website
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