Integrating HTML into vBulletin skin / template

[sparklywater]

I have recently installed the 'Webtemplates' modification for my forum, which allows integration of HTML code directly into a style / skin's layout. After I edit the HTML page in Microsoft Frontpage and then incorporate the HTML code into the template, the resulting page should show the same HTML page as in Frontpage within the layout of the skin (ie. with header / footer, etc.). However, there are some inaccurate font colours, sizes, spacing between lines, etc. which are different from the page shown in Frontpage. I was told by someone that this could be due to a 'clash' between the CSS of the HTML page and the CSS of the skin / style template and that I would need to edit the custom HTML to make it work with the CSS of the style template. I have no idea how to do this so can somebody please give me some guidance on how to get the code to work properly?