stylesheet issue joomla

We have some html content we created for our joomla website. The html has a stylesheet and when we add the html to the static content page in joomla it messes up the joomla templates menu as the stylesheets are getting confused. We need someone to look at the html and styleheet we created and fix it so when we add it to the content page in joomla it reads the correct styles and doesnt change the template menus. We need this done ASAP. This should be a very simple project for someone that knows how to edit stylesheets. Payment made as soon as shown to be working.