Due to some problems on server my website were down for atleast 24 hours, and had some problems frequently 2 days after that. Now according to Google Webmaster tools, I have 200 unreachable pages (error 500). 1- Please help me, that how can i solve this problem, to make these pages crawl again. 2- Does this outage had effect on my SEO ? is it possible to compensate it? Did i lost a very important thing by these outages ?
Its because they are not getting crawled when your site is down, wait some more time it will get back.
just wait till google robots will visit your pages again. you can speedup the process by obtaining links to these pages from other websites.
You should be fine. You won't lose anything from 1 to two days of downtime - Google knows that sites sometimes have access issues. But, anyways - Are you using google webmaster tools? If not, add your site there.
Don't worry dear...........Google will crawl your site again. You can do some more things like: Search Engine Submission, or creating sitemap and then submit in Google Webmaster tool