Google decreasing from 1st position

Hello to all warriors. I would like to say thank you to all for the help you might give to me. I have a website that i built in year 2005. It always kept the 1st position on first google page, yahoo, altavista,portuguese search engines, for the most profitable keywords for me, until two months ago. Two months ago, the website started to decrease positions and it is now on the 5th position on google. In 2005 the website was made with frontpage. Two years later i transformed it in joomla. It kept the positions. In face of this i would like to ask some questions and advices are welcome also:

1 - I found some online seo tools to check the website like rankingtoday.com and seositecheckup.com but they give different results and also the websites that are my competitors and are higher than me on google get worst results on this online seo tools, so, in you opinions, are this tools trustable?

2 - What are the best and trustable online tool or website to make a seo check?

3 - What can be causing this decrease? If someone detect any serious problem on the website, please tell me.


Very important points:

1 - i will write here the url of my website cause i don´t sell anything online. It´s a portuguese companie website that only sell music services so it cannot be considered spam to put the url here, i hope. the url is ibermusics.com

2 - I´m still on 5th position of google´s first page and i´m not putting this thread here cause it is a big problem to be on 5th position. I know it is still a good problem to be in this position but, i´m worried with the possibilitie of decreasing more and more and turn into a big problem for my company.

Any helps will be welcome and i thank you in advance.

Warm regards

Theman2009