Why do all those SEO and web analysis TOOLs presented different Data?

I was analysing our website with different tools including opensitexplorer, moozrank, statscrop, linked checker, seo majestic, semrush, woorank, and so on. And they all have different results to the exact same website. For example, some of them count 17 backlinks, other count 200 backlinks, then there are 14 Facebook likes and then 2 Facebook likes, and so on. The only consistent result were our CSS and HTML errors I found on some tools (25 CSS errors and 19 HTML errors).

Why is that? Could it be that those tools are not reliable?

None of these tools will give you an accurate number. Only Google knows the exact number, and they don't share all the data with you (not even in GWT)

They just give you ballpark figures, but unfortunately that's really the best you have to work with.

Because of their algorithm you are getting different result, obviously Google Webmaster Tool give you a detail and updated report but ahrefs.com is much better than other SEO tool to analyze your website. If you are looking to track your rank then Ezee Rank Tracker is the good tool which I'm also promoting because its easy to understand and give me exact result of SERP in 3 search engines.

Hello

Each service you try will have a different capacity for collecting data.

Some services may have powerful servers - read more money - to check data/metrics; so they can provide users with more detailed results than competitors. Other services, however, may not have as much to spend on servers, so you'll likely get less data from them.

I'll manually go through SERPS until I find where my site is and make a note of its position on a daily basis.

If you want to be thorough, you could always mark its position three times a day (morning, noon and night).

No tool is going to give you an exact number, but they'll give you a rough estimate. I usually find one tool I'm comfortable with and stick to it.