Firstly, I'd like to say you are gooooooorgeous!!! Does anybody say you look like a movie star? The Anne Jacqueline Hathaway :) Anyway let's back to the question. I know there is difference between possibly and probably in English, however it doesn't has any difference in Chinese. If you want to say it in the same way just like in English, here is your way to say it: 1. possibly (less unlikely to happen than probably): 我今天也许（或许，可能）会去你家如果不下雨的话 （天空很阴，非常可能下雨） 2. probably: 我今天也许（或许，可能）会去你家如果不出什么意外的话 （这里就基本上90％会去他家了，因为意外通常指那些不太容易发生的事，只是just in case，这样万一爽约也不至于太难看） 所以我们要表达不同意思时，不是靠词，而是靠背景，和后面加的句子来体现出有多大的可能性

well, i don't think there are some difference between these two words in our daily life. We used them as the same way. They both means "things probably can not happen ". Wish it is helpful.

差不多。 或许隐含着一个选择的过程，不这样，就那样。 It is alomst the same . But when you use "或许" ， it means you have a A choice ,and also a B choice . Do you know , you look like a famous star 姚晨. I like her very much . you can see her photo hier : links http://image.baidu.com/i?ct=503316480&z=&tn=baiduimagedetail&word=%D2%A6%B3%BF&in=18520&cl=2&lm=-1&pn=7&rn=1&di=15166487430&ln=2000&fr=&fmq=&ic=0&s=0&se=1&sme=0&tab=&width=&height=&face=0&is=&istype=2#pn7&-1&di15166487430&objURLhttp%3A%2F%2Fwww.wwwwang.com%2Fuploadfile%2F2011%2F3%2F14%2F20110314151845631.jpg&fromURLhttp%3A%2F%2Fzhrww.wwwwang.com%2Fcontent%2F20113%2F1486007.shtml&W998&H748

First,there are not a big difference between in general.And we could use them in the same situation. However,I want to tell you that "或许"emphasizes the result or the possibility after that than "也许".In other words,""just means there is another possibility. I hope you can understand.^;^

都表示不肯定，个人感觉没什么区别，可以随便用。 u can interchangeable them in all contexts, they are the same meanings, both means not sure.