How we can check our website is blocked or our url is banned in some directory, forum or bookmarks site. Yesterday I was submitting my website on some social bookmarking sites, I saw more than 7 websites had blocked my url or banned and I was not able to bookmark there. Is there anything we can do to unblock our website there ?
If you are talking about other websites blocking your website then you can probably look in their help section on creiterias used to block certain websites.
Some websites use google's malware list to block certain websites. This you can check by checking your website URL against this list from google and if your website indeed show up on google's malware list, then first check your server/website logs and all files on your site. There might have been an attack on your website and some hacker might have installed some malware spending software on your website. Once you have cleaned out your website then you can register with google as webmaster of website and request for your website to be removed from malware list.
You can also mail to customer care/webmaster of website which is blocking your website.
For checking if a corporate blocks your website or not then you need to know which firewall software they use. Then you can test if your website is blocked by that software. Obviously, if you have some friend with that corporate then you can ask him/her to check if your webasite is blocked in corporate or not.
Lastly, check if IP address of your web server is not gettiing blocked due to some previous DoS attack from your IP address (which may happen in case your server was compromised and became a part of botnet)
Just use the webmaster tools of engines.
For example, the Google webmaster tools show you so many things about your website like malware etc. You can just search about your site in google and see if it is listed or not.
Also, there are some online services which check for links in search engines about your websites.