I have downloaded and installed Sitemarvel Bangla font. I could read all Bengali pages on your site. But now I cannot read any Bengali pages nor can I use BanglaWriter or eBaarta. Additionally, in the 'are you prepared for Bengali pages' page, I can see a green message with a square box next to it saying I want to download font. Somehow the browser must think I have not downloaded Sitemarvel Bangla font.
Yes, you are quite right in assuming that the browser is confused! There are a number of reasons why this might have happended: when you downloaded, you may have turned off cookies, or a cookie write may have failed or something unpredictable may have happened which gave your browser the impression that you have not downloaded (for example, some people wipe out cookies thus killing all saved memory variables for many sites). See, cookies must be allowed to be written (and be left unharmed) to ensure that all memory variables can be saved there and reloaded at a later time or date to ensure everything is in order.
Cookies are safe. Cookies were invented to ensure that unscrupulous homepage authors cannot vandalize your computer by writing on your hard disk or removing files etc. The cookies are written by the browser in its own real estate or disk space on your computer. Under no circumstances can a cookie damage your system or files. If you deactivated the cookie facility the sytem cannot write the fact that you downloaded and installed this font. So it condsiders that you haven't got the font.
Remedy: activate cookie (if not already done so) and download Sitemarvel Bangla font once again. If you could read Bengali of this site before this latest download (that is the font is already correctly installed on your sustem), then you may wish to skip the install process. The cookie will now recognise you as a Bengali reader.